Site is an important factor affecting the inter-specific competition of plants. This paper focuses on the correlation between competition intensity, main competition species and site factors, exposes the influence of site factors on interspecific competition, and provides theoretical guidance to conservation of the endangered Japanese yew. The result shows that: the main competition species of Japanese yew in current stands were Tilia amurensis, Abies nephrolepis, Acer mono, Pinus koraiensis, Acer tegmentosum, Betula costata and Acer ukurunduense, and that the majority of competitors were species with lower DBH. Along the site gradient, the competition intensity and competitor type changed notably. The Japanese yews on shady sites suffered 3.27 times greater competition pressure than individuals on sunny sites. On top slopes, as opposed to bottom slopes, the interspecific competition pressures of Japanese yew increased and the competition intensity and type of main competitors changed. The same situation occurred with increasing slope gradients. Elevation, however, had no notable influence on interspecific competition