Abstract: Cephalcia chuxiongnica is one of the important defoliator pests in coniferous forest in Yunnan province, and which mainly infested Pinus yunnanensis. The spatial distribution pattern of C. chuxiongnica larvae on topsoil in P. yunnanensis stands was surveyed and determined using aggregated indices and Iwao’s m^*-m regression mode and power law of Lloyd. The results showed that C. chuxiongnica larvae was the pattern of aggregative distribution. The spatial distribution pattern of C. chuxiongnica larvae could be described by negative binomial distribution. Investigation result of horizontal distribution and vertical distribution showed that there was no significant difference in larvae density of C. chuxiongnica on overburden in P. yunnanensis forest. Theoretical sampling equations were N_0.1=6 788.11/m+3.85,N_0.2=1 697.03/m+0.96,N_0.3=753.98/m+0.43, which were the estimated sample size for different densities of larvae with an accuracy of 0.1, 0.2 and 0.3, respectively. These results provided a basis for the scientific sampling of C. chuxiongnica larvae in the forest. According to the above equations, 20, 50 and 80 sampling units should be sampled when the density of C. chuxiongnica is assumed to be 86, 35 and 22 individuals per sampling unit.