The survey was carried out by Politics and International Relations students at Royal Holloway, University of London.
The former Conservative leader, who died last April at the age of 87, was valued for her decisiveness by MPs who took part in the poll.
The Iron Lady topped the survey in which MPs rated every leader between 1945 and 2010, a statement on the University website said.
MPs were asked to evaluate how successful or unsuccessful they thought each prime minister was, with answers being recorded on a 0-10 scale.
Also Read
Another former Labour prime minister, Tony Blair (6.8), came third ahead of the Conservative Winston Churchill (6.5).
MPs judged Blair's rival and immediate successor, Gordon Brown (3.3), to be the least successful occupant of 10 Downing Street.
MPs cited decisiveness as a more important characteristic than intelligence, principles or honesty.
"Thatcher has a unique place in the minds of British MPs. As well as being judged the most successful prime minister, she also elicited the widest range of responses," Dr Nicholas Allen, Senior Lecturer in Politics at Royal Holloway who organised the study said.