Background: The sophistication of students' conceptions of science learning has been found to be positively related to their approaches to and outcomes for science learning. Little research has been conducted to particularly investigate students' conceptions of science learning by laboratory. Purpose: The purpose of this research, consisting of two studies, was to explore Taiwanese university science-major students' conceptions of learning science by laboratory (CLSL). Sample: In Study I, interview data were gathered from 47 university science-major students. In Study II, 287 university science-major students' responses to a CLSL survey were collected. Design and methods: In Study I, the interview data were analyzed using the phenomenographic method. Based on the findings derived from Study I, Study II developed an instrument for assessing students' CLSL by exploratory factor analysis. Results: Study I revealed six categories of CLSL, including memorizing, verifying, acquiring manipulative skills, obtaining authentic experience, reviewing prior learning profiles, and achieving indepth understanding. The factor analysis in Study II revealed that the "verifying" category was eliminated, but found another new category of "examining prior knowledge." Conclusions: This study finally proposes a framework to describe the variations of CLSL, consisting of three features: cognitive orientation, metacognitive orientation, and epistemic orientation. Possible factors influencing students' CLSL are also discussed.