Alnus nepalensis and Litsea glutinosa are the two common trees in the habitats of black-crested gibbons (Nomascus concolor) in Wuliang Mountain of Yunnan Province. With the nearest neighbor method and Heygi's competition index model for individual tree, this paper analyzed the distribution patterns of the two populations and their competition. The results showed that A. nepalensis had a random distribution at its different growth phases, while L. glutinosa, the companion species of A. nepalensis, exhibited the trend of random distribution-clumped distribution-regular distribution. Interspecific competition and biological characters had significant effects on the distribution patterns of A. nepalensis and L. glutinosa. Regression age structure was observed in A. nepalensis population, while increasing age structure presented in L. glutinosa population.