I was graduated last March 2011. Is this a correct grammar?

It's better to write, "I graduated last March."

Or "I graduated in March 2011."

1. The passive is not needed.
2. "last March" and "March 2011" are redundant.

No, the sentence "I was graduated last March 2011" contains a grammatical error. Instead, you can say "I graduated in March 2011."

No, the sentence "I was graduated last March 2011" does not use correct grammar. To express the idea that you completed your graduation in March 2011, you should rephrase it using the active voice, saying "I graduated in March 2011." In English, we typically use the verb "graduate" in the active voice, rather than the passive voice.