Being potential rivals, the two similar tits, Rufous-vented Tit (Parus rubidiventris) and Coal Tit (P.ater) are occurred in the same habitat at the plateau of Wawushan in Sichuan, China.During the breeding seasons of 2010 and 2011, we studied the mechanism of their niche separation and coexistence.For vertical distribution, the niche width of Coal Tit (5.237) was significantly higher than that of Rufous-vented Tit (2.792), however, there was no significant difference for horizontal distribution and active matrix, with the total value of niche overlap over 0.7 in three dimensions.But the two species of tits showed preferences and focused on resource utilization of all these three dimensions.The parameters of most body’s measurements for these two tits are significantly different, except for the bill width, which might be the results from environmental adaptations.There was no significant difference for all the parameters of the nest-site selection of the two species, indicating that appropriate cavity nest sites might be their main competition factor.The population size of these two species may vary with their residence types.We suggest that the separation of spatial niche and food niche, appropriate population size and ratio might be the important factors for their coexistence.