This research aims to compare the effect of the implementation of three levels of inquiry: level 2 (structured inquiry), level 3 (guided inquiry), and level 4 (open inquiry) toward science concept understanding of elementary school teacher candidates. This is a quasi experiment research with pre-test post-test nonequivalent control group design. The population of the research was the students of Elementary School Teacher Education of University of Mataram who took the science education program. The sample of this research was 154 students taken by using cluster random sampling technique. The research instrument was a science concept test. The data were analyzed by using ANCOVA. The results showed that the implementation of open inquiry had the highest score of science concept understanding and was significantly different from the scores of the structured inquiry and guided inquiry and traditional strategy, while the scores of the structured inquiry, guided inquiry and traditional strategy were not significantly different. Thus, the conclusion of this research was that the implementation of open inquiry has a significant effect, while the implementation of structured and guided inquiry did not have a significant effect on the increase of science concept understanding of elementary school teacher candidates.