The invention provides a method for detecting a genotoxic agent by the utilization of Pseudorasbora parva and belongs to the field of chemicals safety evaluation and environmental monitoring. The method comprises the following steps: (1) processing Pseudorasbora parva by exposure treatment by the use of a water sample to be tested; and (2) carrying out single cell gel electrophoresis assay by using hepatic cells of Pseudorasbora parva processed after exposure treatment, detecting and counting cell tail length, DNA content and tail moment, and drawing a dose-effect curve. Through comparison between the result and a blank control and a positive control and through the dose-effect relationship, genetic toxicity of the test sample is determined. The detection method of the invention can sensitively and rapidly determine genetic toxicity of chemicals. The invention provides a China native species-based detection method for chemicals genetic toxicity evaluation and environmental genetic toxicity monitoring.