Competition is one of the basic driving forces to form a specific community structure and constitute a distribution pattern. The spatial distribution and size of tree species are not independent of each other, but they are widely affected by the competition process. We set up a representative natural secondary forest restoration sample plot in Greater Khingan Mountains using the nearest neighbor distance G(r) function, double correlation function g(r), and the marker point pattern analysis method based on individual breast diameter. The distribution pattern, correlation and competitive effect of Lgmelini in different life history stages were analyzed. Results show that:the larix gmelini population has different distribution patterns at the different development stages, and it also has different distribution patterns at different research scales but the same development stage. There is potential competition in the population, while the competition is related to age class and research scale. The aggregation distribution of young individuals at a small scale (r<5m) is caused by diffusion restriction and competition. There is a strongly positive correlation between adult and young individuals in the population, and the adult individuals have an obvious sheltering effect on young individuals at a small scale. Marker pattern analysis method is highly sensitive in detecting competition in plant communities.