Based on the data collected from the sampling plot with an area of 1 hm2 at the Experimental and Management Bureau of Jiaohe in Jilin Province, this paper analyzed and researched the community structure, biological diversity, spatial distribution pattern and interspecific association between tree species populations in a mixed deciduous broadleaved forest. The results indicated that there was no obvious dominant order among tree species populations, and the indices of tree species diversity such as Shannon-Wiener index (H'), Pielou evenness index (E) and Simpson ecological dominant index (D) were all low. Shrub and herb species diversity indices were also not high. The spatial distribution pattern of five dominant tree species all presented aggregative. Based on 2 x 2 contigency table, the interspecific associations of 15 tree species in the community were examined by means of chi2-test, together with the association coefficient (AC). The results showed that there were 14 species pairs in 15 species showing significantly negative association. The proportion of species pairs showing negative association was much more than that of showing positive association. It could be deduced that the community was instable and at the stage of autogenic succession from soft deciduous broadleaved forest to hard deciduous broadleaved forest, and then, the Korean pine broadleaved forest.