As part of small project i want to measure temperature of the distant star on basis of optical observations. so by what exact method i can do it? which instruments will be necessary? what is the precision of the experiment?
To measure the surface temperature of a star it is used is it's black body spectrum. You would have to get the light curve of the light from tat star and then by checking it's peak you could guess its temperature.
I really don't know which instruments to use to get the light curve from a distant star but you could use a tool like this one for the final conversion: http://astro.unl.edu/naap/blackbody/animations/blackbody.html