In this paper, CiteSpace is used to conduct metrological and visual analysis of the core journals of blended learning research (2003-2021) collected by the China National Knowledge Infrastructure (CNKI). The results show that the number of studies on blended learning in China is increasing year by year, which indicates that the research on blended learning continues to attract attention and that blended learning is not yet mature. The research hotspots include the basic theory research of blended learning, teaching design research, learning resources and platform construction, and application practice research. The research frontiers include analysis and application research based on a specific learning platform, application research of blended learning in a certain field, and instructional design research. The development trend is changing from basic theory research to teaching application practice from focusing on teachers' teaching to students' learning.