World number two and top seed Serb Djokovic raced to the first set against German Mayer without facing a break point then needed just the one break chance in the second set as he emerged a 6-1 6-4 winner.
Mayer failed to make the most of his two break points in the second set as the match was completed in under an hour.
Earlier Tsonga kept alive his hopes of qualifying for November's season-ending World Tour finals in London.
Third seed Tsonga, ranked number seven in the world, won the first set 6-1 and was up 4-1 in the second when his Spanish opponent retired due to a left wrist injury.
"I played really well," Frenchman Tsonga said after reaching his 15th Tour final.
"I felt really good on the court. I'm just happy today with my game. I'm sure I will play good tennis in final."
Tsonga, who won titles in Metz and Doha this year, will add crucial ranking points in Beijing that will boost his chances of qualifying as one of the top eight ranked players for London.
British pair Colin Fleming and Ross Hutchins lost 6-2 6-3 in the semi-finals of the men's doubles against Carlos Berlocq of Argentina and Denis Istomin of Uzbekistan.