This research aimed to explore the conceptual structure of chemical equilibrium in upper-secondary school students using factor analysis. Research on chemistry education has shown that chemical equilibrium is an important but difficult-to-understand topic. Exploring the conceptual structure of chemical equilibrium among students will help chemistry researchers and educators to conduct more targeted teaching practices. Based on a survey of chemistry research and teaching practice experts, a high-quality concept pool composed of 24 relevant concepts was developed. Next, a survey involving a total of over 700 twelfth-grade students from five upper-secondary schools was conducted, and a factor analysis was utilized to determine the conceptual structure. The results showed that a three-factor model and a five-factor model with 15 relevant concepts were all accepted as the conceptual structure for students. The new form of conceptual structure in this research helps understand the features and categories in students' latent organization of concepts. Also, it may be revealed that factor analysis can be utilized as an approach to exploring students' conceptual structure.