I hate to go to parties.but i should go tomorrow to a wedding with my parents.is there any medicine for social anxiety ?

Anxiety treatment: The best way to handle social anxiety is to monitor your thoughts and go see a psychologist who specializes in anxiety treatments. Especially CBT therapy. Hypnosis is also good.

Short term fix: Ask your physician about propranolol if you have time. This may work -- people afraid of speaking in public use it. Think about the purpose of going to the party -- the meaning it has for you and others. Long term, get social-skills training, have a coach teach you how to talk to strangers, understand your own feelings and possible cognitive distortions / past habits to be overcome, with time.