Hi,my name is suprim jha I came here by h2b visa and I'm going back my country,if I close my social security,then do I get any refund?

Negative; your work visa made you liable for the tax, but the limited duration of the visa makes it virtally impossible for you to qualify for benefits, and no refund is available.

It is patently unfair, but no one has EVER said taxes in the U.S. is fair.

On work visa you must pay taxes just like U.S. citizens and residents.