Spermicidal effect of Jieze No. 1 (JZ1) in combination with nonoxynol-9 (N-9) was examined in vitro. The minimum spermicidal concentration of JZ1 decoction, N-9 and their mixture solution in 20 s and 3 min were examined by improved spermicidal test of Sander-cramer in vitro. The percentages of progressively moving spermatozoa, moving spermatozoa and viable spermatozoa were also observed 20 s, 3 min and 30 min after the addition of the liquid medicine. Our results showed that sperms did not recover their activities in a revival test when the minimum spermicidal concentration of either JZ1 decoction, or N-9, or the mixed solution of the two agents, was used. N-9 (JZ1 in the mixed group) showed significant differences in the percentages of progressively moving spermatozoa, moving spermatozoa, and visible spermatozoa in 20 s, 3 min, and 30 min, when compared with N-9 alone (P < 0.01). We are led to conclude that JZ1 decoction can improve N-9 spermicidal action in vitro, and when used in combination with N-9, it has synergic effect.