Despite the importance of undergraduate research for student learning and development, not enough work has been done to clarify its effects in different disciplinary contexts. Using data from the China College Student Survey, this research adopts Becher and Trowler's theory of discipline classification to understand the relationship between undergraduate research and students' learning outcomes in different disciplines. It indicates that first, contributing to journals/conferences correlates with students' self-reported learning outcomes in Physics, History, and Engineering, but these relationships can be explained by process-centered activities, except in Physics. Second, early-year undergraduates' learning outcomes are relatively weakly related to conducting research with faculty in pure disciplines. By contrast, such relationships are distinct in applied disciplines. Third, in soft disciplines, participating in competitions significantly correlates with more types of students' learning outcomes than conducting research with faculty, while in hard disciplines, they both play quite important roles. It makes recommendations for future research and practice, which enrich insight into how universities can best engage undergraduates in research.