In a statement, the Academy said the 94th Oscars had been "overshadowed by the unacceptable and harmful behaviour we saw Mr Smith exhibit on stage".
Smith has apologised for his actions and resigned from the Academy.
The actor hit Rock for joking about his wife's shaved head, a result of the hair-loss condition alopecia.
Less than an hour later, he was awarded the best actor award for his role in "King Richard", where he played the father of tennis stars Venus and Serena Williams.
