I saw many cricketers which play for another country instead of his own country.But is it necessary to get nationality of this country for playing international cricket for this country?
Cricketers who play for other countries are most likely born and raised in that country. For example, Hashim Amla is an Indian by origin, but was raised in South Africa and gained nationality of South Africa. Thus, he is in the national team. If any player does not have a nationality of the country they wish to play for, then they most probably aren't able to.