The formation and maintenance of biodiversity, that is, plant community assembly mechanisms, has been a central issue in community ecology for decades. The deterministic process of plant community assembly is mainly the result of ecological filtering, including environmental and biological filtering (interspecific competition and intraspecific functional trait variation). Previous scholars have developed a large number of theories, methods, and models to explain and verify the impact of ecological filtering on community assembly. However, uncertainty remains about the role of ecological filtering mechanisms in different scales, and the decomposition and quantification of various factors in the ecological filtering mechanism. In this paper, we made a detailed review on the research progress of environmental filtering, interspecific competition, and intraspecific functional trait variation. We further proposed a guide to focus on the decomposition and quantification of ecological filtering mechanisms, development of comprehensive research methods, effects of spatio-temporal dynamics on community assembly, understanding the commonness and personality characteristics of different community assembly mechanisms, and emphasizing the integration with other ecological processes and community building mechanisms. These attempts may help us better understand the role of the ecological filtering in plant community assembly.