WW2 era soviet ROKS series flamethrowers are listed as in likely
North Korean and/or chinese service during the korean war.
http://www.kmike.com/Enemy%20Weapons/Frames/253.htm
I have also found several references of flamethrowers being in service with north vietnamese army sappers during the Vietnam war.
I think it is a safe bet that the chinese had some flamethrowers in service before 1979, though numbers and models are debatable.