Abstract: A numerical investigation was conducted to study some key parameters of multi-injection combustor,including swirl numbers,space between venturis,distance between the dome and the diffuser.The influence law of these parameters on the multi-injection combustor's recirculation zone was concluded.This shows that,with increase of the swirl number,the reverse velocity of the recirculation zone will rise.When the swirl number increases from 0.82 to 1.24,the maximal reverse velocity is 52% greater and the recirculation zone is 34% longer.When the space between venturis changes from 0 to 0.4 times the exit diameter of venture,the radii of recirculation zone is 33% bigger and the length is 43% larger.With the increasing area of inlet of the diffuser and the growing distance between the dome and the diffuser,the distribution of the flow is more uniform.