Abstract: A test method for the combined toxicity of chlorpyrifos and butachlor, which comprises the following steps: A. Experimental organisms: The zebrafish wild type AB strain is used in the experiment. After the purchase, it is domesticated in the laboratory, and the experimental fishes for collecting fish eggs have been kept in this laboratory for more than 1 month. Through the combined toxicity test and single pesticide test, it is convenient to increase the reference data and improve the mutual comparison of the data according to the impact of different environments and different agents on the animals. Better balance and offset the effects of irrelevant variables, making the experimental results more convincing. The probit analysis method is used to calculate the pesticides on larvae based on the number and the time of death of fish larvae, and the data is reasonably analyzed and processed to avoid reliance on single effect.