Hello Mr. bhalchandra laxman padwal,

I think you need to make sure each input to the multiplexer is driven by a low impedance device such as a OpAmp hooked up as a unity voltage follower [1](high input impedance and low output impedance).

I had a similar problem using a 4067 sixteen input multipler IC. I had some inputs floating while others inputs had signals hooked up to them. The entire circuit acted erratically and was corrected when all inputs to the multiplexer was fed with a low impedance source.

Good luck,

Charles Bannister