Water conserving forest in the Laotudingzi Natural Reserve of Liaoning Province was investigated. Based on the important values of population, a study was performed to discuss the interspecific relationships among 16 main tree species by χ²-test, Ochiai association index, Pearson's correlation coefficient and Spearman's rank correlation coefficient. Results showed that the connection degree of most species-pairs did not reach a level of significance and the proportion of species-pairs which had highly significant or significant correlation was less, indicating that the interspecific relationships among forest tree species were loose and did not form a significant overall association, so the community was relatively stable. Compared with χ²-test, Ochiai association test and Pearson's correlation coefficient test, Spearman's rank correlation coefficient test was sensitive. According to the analysis results and combined with the tree species population biology and ecological adaptations, the 16 main tree species in the water conserving forest can be divided into three ecological species groups. The ecological requirements and resource use patterns of tree species within the same ecological species group are similar, exhibiting a close connection between the tree species and however, there is a loose coupling between different ecological species groups.