The Briton only needed one set to reach the last four, but beat the Swiss 6-4 6-2 to top the John McEnroe Group.
Murray extended his winning streak to 22 matches and goes on to face Milos Raonic on Saturday.
Djokovic also won all three of his group matches, and Murray must at least match his results at the O2 Arena to end the year at the top of the rankings.
“The first set was tight. There weren’t many chances,” said Murray, 29.
The Scot knew he only required one set, while Wawrinka was really in need of a straight-set victory, lending the contest an added air of tension from even the early stages.
Wawrinka, 31, blasted four winners in the opening game but could not make the breakthrough and Murray capitalised in game seven.
Wawrinka framed a forehand to drop serve at the start of the second and his challenge was all but over, as Murray raced 4-0 clear and closed it out after one hour and 26 minutes.
Source : Internet