Gender differences exist in the disciplines of science, technology, engineering and math. There are differences between male and female undergraduates in the learning of various subjects. This paper analyzed the gender differences caused by intellectual and non-intellectual factors, such as math ability, verbal ability, spatial capability, learning motivation, learning interest, and learning attitude. On the base of the scores of theoretical physics, we analyzed the gender differences of undergraduates major in physics, and put forward teaching strategies for the improvement of theoretical physics.