The secondary coniferous and broad-leaved mixed forest in Changbai Mountains is one of the typical secondary forest types in northeast China. It is in an important stage of succession to the climax vegetation, i.e. broad-leaved Korean pine forest. Through a comprehensive analysis of community dynamics in the secondary coniferous and broad-leaved mixed forest in Changbai Mountains, we can provide the scientific support for forest conservation, restoration and sustainable management. Based on a 5.2hm² dynamic monitoring plot in Changbai Mountains in 2005 and 2017, all woody plants with DBH ≥ 5cm were investigated as study objects. The non-spatial structure dynamics including species composition, species diversity, DBH structure and density structure, and the spatial structure dynamics including the spatial distribution pattern, tree species mixed and trees competition were analyzed. The results showed that the total number of individuals in the community decreased from 6614 to 5884. Forty-two species of the plants belonging to 25 genera and 13 families were found in 2017, which increased by 2 genera and 2 species compared with those in 2005. These indicated that the variation of species composition and diversity was small. The average DBH increased from 14.4 cm to 15.5 cm. Although the community maintains an inverted "J" type of DBH structure and a positive regeneration, the number of individuals at each diameter level was significantly reduced. The coefficient of DBH variation and DBH Gini index increased from 0.77 and 0.37 to 0.79 and 0.38, respectively, indicating the complexity of the community increased. The stem density of community individuals decreased from 1272 to 1132 per hectare, and the stand density increased from 33.12 m²/hm² to 34.74 m²/hm². The spatial structure of the community did not change during the two censuses. The horizontal distribution pattern of the community was randomly distributed (W=0.51). The degree of size differentiation was moderate (U=0.50). The mingling degree was strong (M=0.76). Those indicated that the spatial structure was stable and ideal. Furthermore, the change trend of community structure was compared at both plot and 20m×20m subplot scales. We found that most of the indicators had the same trend on both scales. In conclusion, the non-spatial structure of the secondary coniferous and broad-leaved mixed forest showed a positive succession trend, while the spatial structure of the community remained stable. The community structure had not essential changes within 12 years. In the future forest management, the understory trees such as Acer pseudosieboldianum and Acer mono could be appropriately removed to provide space for the growth and regeneration of climax species such as Pinus koraiensis, Quercus mongolica and Tilia amurensis.