FSS Transmission/ Reflection Curves

Can anyone tell that, what is the difference between the FSS Transmission/Reflection characteristics with and without ground plane?

I assume you mean for normal incidence. Think of a transmission line, with the incoming wave as a source, and the ground plane as a load, in this case, a short. The short translated over a short distance of the dielectric height will appear to be an inductor in parallel with your FSS. Of course, your FSS will behave differently too, due to different field profiles. I can't say much more without specific information.

actually i wanted to ask what difference the ground plane will make to the reflection and transmission.

Again, I'm not sure if you mean for normal incidence, but obviously if the ground plane is a PEC the FSS will not have any transmission.