i have build a quad copter with kkmulticopter v5.5  board with flysky fs-ct6b rx tx ...... successfully calibrated the ESC with YAW at 0% but when i restore yaw to 50% and try to arm, it  doesn't arm at all.....please help..

How are you arming.
By means of sticks only or
sticks +trims.
in this tx you have to use both sticks and trims so as to arm it.
Yaw can be made zero by moving yaw stick all way to right along with trim pot and similarly while disarming, do the opposite.
If this doesn't work try to dedicate one channel for arming.

at YAW 0 it throttle works without arming but others doesn't ie elevation aileron or rudder.. by the way what it means "" in this tx you have to use both sticks and trims so as to arm it. ""

Take throttle trim to zero and try. It should work..

You face this problem when you use this tx or similar kind with analog trims rather than digital trims.
When arming if you move yaw left and right they dont go to their max and min values. In order to do that you have to use trims of particular stick.
When you want to arm move yaw stick toward its extreme position and also the trim of yaw. By doing this the yaw output will be zero.
I don't recommend this tx for multi copter because the sticks wont return back to centre when you change their position.
I faced this kind of problem with this tx.

that means that the when my  TX having zero throttle  the output in the image should be 0% or like in the image

As you lowered the pitch trim in the video, try lowering the throttle one  (left side trim) to the lowest point. Try this...

The image is correct moreover it may go further less than -58% by using the trims available at each stick.

tried but no luck

Try to lower throttle all the way down even you bring down the trim.
Now rudder at left, pull it all the way towards right along with trim to right. That is take yaw to maximum.
Doing this will arm motors.
You can also adjust few things like trimming tx from t6config software.
First thing first : To arm motors we need to bring throttle down to minimum and yaw to maximum.
Try to do this using software t6config.

I have a very little experience with the ct6b.  the first thing to do is gimble calibration with 'digital radio' software.

I hope you binded your receiver with your transmitter....!!!!!
If thats done.......
Then Set throttle trim to zero...And rest of trims to center...
Recallibrate esc.....
And then switch of the quad and then Switch of the transmitter

Then Switch on the transmitter and then switch on the quadcopter....Then try arming it...

One of the possibilities may be as that your throttle may be reversed...So lower your throttle and move stick to left side or right side......See/observe moving to whcih side arms your quadcopter.....!

Other posibility is that you didnt set the CHANNELS(Elevator, Aileron, Throttle and Rudder) OR MODE(4 modes) properly

And yours is set to mode type 1...see the right side in your pic ....

Set the mode type 2(Standard mode- used in India and US)

And please please see the kk board and receiver channels are set properly ie throttle channel of receiver is connected to throttle pins of kk board....

thank you all...now its armed

my quad is Armed now but when i increase throttle all 4 motors doesn't starts at same

I used to face this... have u set any D/R settings? i put it on rates and the quad wouldnt arm... just as a precaution get 12 AWG silicon wire from somewhere, those tiny wires will get burned, so will thick copper wire... i learned it the hardway XP i like the frame and  if all the 4 wont start at the same time then u must calibrate the ESC

What was the actual problem in your case. If you observed !

First you caliberate all ESC's at once.
If problem persists then I think two opposite motors are starting at same time. This is not a problem during flight because your quad is trying to yaw without your input. If so the FC will automatically correct it.

solved: feeling good...
1st: calibrate my esc with min throttle trims
2nd: set YAW to 50%
3rd: turn on transmitter
       set throttle to min with minimum trims too
4th: turn on Quad let everything to calibrate
5th: turn the (Tx)Rudder to extreme  left and its ARMED....


thanks everyone!