Objective To systematically evaluate the multi-generational reproductive and developmental safety of long-term consumption of genetically modified maize expressing cry1Ab / cry2Aj and G10evo-EPSPS protein (double-resistant 12-5) in cynomolgus monkeys. Methods Thirty-six sexually mature cynomolgus monkeys ( F0 generation, 6 males, 30 females) were divided randomly into conventional diet (CK), genetically modified maize (GM), and non-genetically modified parental maize (Non-GM) groups. Animals were bred in a harem system at a male-to-female ratio of 1 ∶ 5. The reproductive performances of the F0 and F1 generations were recorded, and F1 / F2 offspring were assessed systematically for fetal appearance, neurobehavioral development, physical growth, and hematological / serum biochemical parameters. Results There was no significant difference in F0 pregnancy rates (GM group: 32, CK group: 26, Non-GM group: 29; P>0. 05) or overall F1 offspring survival (GM group: 19, CK group: 20, Non-GM group: 14; χ2 = 3. 141, P= 0. 237) among the groups. There was also no significant difference among the groups in terms of reproductive performance of the F1 generation or survival of the F2 generation ( P = 1. 000). No fetal malformations were detected in any offspring. Behavioral neurodevelopmental scores, physical growth trends, and baseline physiological parameters (including 24 hematological and 18 serum biochemical indices) showed no differences among the three groups. Conclusions Long-term consumption of doulde-resistant 12-5 maize had no adverse effects on parental fertility or early offspring development in cynomolgus monkeys, providing important non-human primate evidence for the safety of this genetically modified crop.