Murray’s last outing came at the Davis Cup in Manchester last week and he got off to a strong start in China, winning 7-5 6-3 in the round of 32 contest against the world number 668.
The opening set saw a closely-fought encounter with Mo bouncing back to draw level throughout, but Murray broke serve in the final game to edge the set 7-5.
A tough first game of the second set saw Murray fight back to win the advantage. Mo then levelled, only for Murray to pull away and serve up his 10th ace of the match to win 6-3.
The 36-year-old admitted he struggled in the early stages, saying: “It was a very, very fast court. The conditions were very humid and my opponent played a solid level at the beginning of the match and pushed me while I was trying to adjust to the conditions.
“Once I managed to get ahead at the beginning of the second set I felt a bit more comfortable but it wasn’t easy and a lot of the players have said the same thing.”
Victory means the Scot will now face Aslan Karatsev in the last 16 after the world number 63 beat Matteo Arnaldi in their round of 32 meeting.
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