The genetically modified maize carrying insect-resistant gene and herbicide-tolerant gene has substantial benefits for crop production. The three generation reproductive toxicity of the maize was studied in this paper. One hundred and eighty Sprague-Dawley (SD) rats were divided into three groups which were fed with genetically modified maize (GM) diet, receptor maize (RM) diet, and AIN-93G (AIN) diet (used as control) respectively. The body weight, food consumption, reproductive parameters, hematological parameters, serum chemistry, organ weight, histopathology for the three generations were examined respectively. Minor differences were found between the GM group and the RM group or the AIN control group in terms of reproductive data, hematology, blood chemistry parameters, and organ index, but no macroscopic or histological adverse effects were found or considered as treatment-related. In conclusion, the three-generation study of genetically modified maize DBN9936 with Cry1Ab and epsps genes at a high level showed no unintended adverse effects on rats’ reproductive system.