Taking Chinese listed companies in 2008-2015 as the sample, in this paper we test in detail the impact of female directors on corporate environmental investments. Furthermore, we study the impact of female directors on environmental investment in enterprises with different types of ownership and industry attributes. Empirical studies show that when there are only 1 or 2 female directors on the board, no significant impact on the scale of corporate environmental investment can be seen. However, when the number reaches at least 3, female directors have a significantly positive impact on the scale of corporate environmental investment. This confirms critical-mass theory; meanwhile, we find that the empirical results do not indicate any significant correlation when the variable of female directors is measured by the proportion of female directors and the Blau index of gender balance. Further analysis suggests that in state-owned enterprises and enterprises from heavily-polluting industries, the above findings remain true, while in non-state-owned enterprises and enterprises from non-heavily-polluting industries, the above findings prove false, i.e., that the impact of female directors on corporate environmental investment is not significant. The conclusion demonstrates that the impact of female directors on environmental investment varies in enterprises with different types of ownership and industry attributes.