Experiment on pheromone trap density for mass-trapping of the rice stem borer,Chilo suppressalis（Walker） was conducted in Wuchang of Heilongjiang Province in 2011.The results showed that the mean numbers of male moth captured per tray in treatments with 45,45,and 30 trays per hectare were 76.50,68.00 and 76.80,respectively.The total numbers of male moths captured increased by 49.22% and 32.81% when trap density increased by 50%.The numbers of white head and semi dry spike were 0.67,1.50,2.00,7.33 in the treatments with 45,45,30,0 trays per ha.The control efficiency was 90.91%,79.55 and 72.73%,respectively,and it slightly increased as trap density increased.The authors believe that the density of 45 traps/ha is suitable for most areas in Northeast China at present,and the density should be reduced to some extent where the pest population density is low.