Abstract: The redbelly tilapia Coptodon zillii and the mango tilapia Sarotherodon galilaeus are two invasive fish species in the Shanmei Reservoir, which have become dominant species of the fish community in the reservoir. In order to compare their reproductive traits for developing invasive control measures for the two tilapia species, we monthly sampled fishes from March to October 2021 in the Shanmei Reservoir, and analyzed their reproductive period, sex ratio, absolute fecundity, relative fecundity and egg size. We also analyzed the reasons for their stable coexistence after co-invasion through the reproductive biology of two species of tilapia. Results showed that both populations started to spawn in April, but the spawning activity was peaked in July and June, and ended in October and September for C. zillii and S. galilaeus, respectively. The absolute fecundity of C. zillii was (4009.85±1305.69) eggs, the body weight relative fecundity was (67.32±15.63) eggs/g, and the body length relative fecundity was (31.31±5.03) eggs/mm for C. zillii, which were significantly higher than those of S. galilaeus (1701.85±591.29) eggs, (6.46±0.87) eggs/g, and (8.22±2.33) eggs/mm. However, the mature egg size of C. zillii was significantly smaller than that of S. galilaeus. The sex ratios (female/male) of C. zillii (1.59) and S. galilaeus (1.83) showed non-significantly difference and females outnumbered males in these two species but both ratios were significantly biased with 1﹕1. This study suggested that the two co-invasive tilapia exhibit different reproductive strategies, which should be key factors explaining their dominant abundance and stable coexistence after successful co-invasion. This study can provide implications for the management of the two co-invasive tilapia populations, which contribute to the sustainable development of fisheries resources management in the Shanmei Reservoir.