i have bought a 20 amps ESC but cant match up with the motor.can motor in the attachment works on 3cell lipo  

This motor indeed will work with a 3 Cell Pack
And the 20Amp ESC is sufficient for it.

BTW, would you please explain the following:
"cant match up"

Welcome to RCIndia  

it has been mentioned that 980kv-12v-APC 9*6 gives 730grms of thrust,what will be the diffrence if i use 6*6 APC prop?

A 6*6 prop on a 980kv motor ?

yes,on 980kv motor with 20amps ESC and 3cell lipo

I believe you want to use a smaller prop due to space constraints.
Although you will be using a higher pitch Pitch prop (6 in this case) which sure will give you some thrust but it still won't even be close to what you'll get from a 10x4.7. You will get way less thrust.
A 6 inch prop would have been fine on a 4S Setup. But this motor doesn't support a 4S setup.

If space constraints is paramount then use a higher KV motor props to get optimal thrust.

BTW, what are you cooking mate?
Plane/Quad ?

My plane is a twin engined aircraft about 2.5ft in length and weights nearly 1.5 kg.if I use 2*980kv motors with 6*6 props on 3s will it delivers enough thrust?

use ecalc.ch

Bob8064, is that 2.5 feet or 2.5 meter? what is the material of the plane? for a 2.5 feet plane even 400gms is too much in my opinion.
Where do you live in chennai?

Ashok.P

It's 2.5 feet built with Styrofoam twin motor aircraft.

Have you weighted it to 1.5Kg? what battery and motor are you using.
1.5KG is really too much for a 2.5FT plane unless you are building some king of jets. plans, pics of the plane please, BTW, is this your first plane, and where do you live in chennai, there are a bunch of guys(us) who fly towards south chennai, you can meet up with us if you need any help.

i don't know the exact weight.i hav attached the aircraft plan plz check it out,i'm going to use 2*980kv motors,2*20 amps esc,2200mah 3s 20c lipo,4*9g servo motors,styrofoam,2mm corbon fibre rod,covering film etc...i'm out of station now i can't meet you guys..