Abstract: To investigate the developmental effects of combined exposure of azoxystrobin and selenomethionine on aquatic organisms, a semi-static test method was used to determine the developmental toxicity of combined exposure of azoxystrobin and selenomethionine in equitoxicity ratios on embryo and larvae of zebrafish as aquatic model species, as well as the effects on related enzyme activities. These results showed that: after the combined exposure of azoxystrobin and selenomethionine with different concentrations (0.1+0.2, 0.25+0.5, 0.5+1.0 and 1.0+2.0 mg/L) (the mass of selenomethionine was calculated as the mass of selenium, and the same below), the embryos showed a decrease in the autonomic movement frequency, a decrease in hatching rate, an increase in mortality rate, and a decrease in heart rate. At the same time, and body length of hatching larvae was significantly inhibited with an obvious time-dose-effect relationship. Compared with the control group, the activity of catalase (CAT) was significantly decreased in different combined exposure groups (0.0005+0.001, 0.005+0.01 and 0.05+0.1 mg/L), and the high concentration combined exposure group (azoxystrobin 0.05 mg/L and selenomethionine 0.1 mg/L) showed the most significant inhibitory effect (P < 0.01), while it had no significant effects on the activity of superoxide dismutase (SOD). Compared with the control group, the combined exposure group of the highest concentration (0.05+0.1 mg/L) significantly inhibited the activity of the mitochondrial respiratory chain complex Ⅲ(P < 0.05), while the combined exposure groups of other concentrations had no significant difference. The results suggested that the combinations of azoxystrobin and selenomethionine (0.1+0.2, 0.25+0.5, 0.5+1.0 and 1.0+2.0 mg/L) could cause developmental toxicity effects on zebrafish embryo and larvae, however, the combinations of azoxystrobin and selenomethionine at actual environment-related concentrations will not cause any developmental toxicity effects except for inhibiting the activity of CAT. These results can provide data support for monitoring the concentrations of azoxystrobin and selenomethionine in aquatic environment and the ecological risk assessment of their combined exposure in the future.