Abstract: Analysis of community assembly rules plays a crucial role in understanding species coexistence and the maintenance of biodiversity of the community. We conducted field investigations and statistical analysis on 374 plant plots(20 m×30 m) in the east of Yanshan Mountain, and used Multiple Regression Tree(MRT), phylogenetic index and Gaussian kernel density estimation(Gaussian KDE) on data collected from study sites to explore its community assembly rules. The whole community could be divided into five formations, including Vitex negundo var. heterophylla, Quercus aliena, Q.mongolica, Q.variabilis and Fraxinus chinensis. Among these forms, environmental filtering mainly influenced the community assembly process in V.negundo var. heterophylla, Q.aliena and Q.mongolica, competition controlled the speciation in Q.variabilis, while in F.chinensis, the pattern had been changing from environmental filtering to competition. In addition, Gaussian KDE was introduced to illustrate net relatedness index(NRI) and nearest taxon index(NTI) values, providing a new intuitive perspective to explore the argument between niche-assembly and neutral processes.