Abstract: To explore the influence of stage II waterway regulation works of the Dongliu channel in lower Yangtze River on the spawning flow condition of Four Major Chinese Carps, based on the existing 2-D flow mathematical model and the habitat suitability index (HSI) of Four Major Chinese Carps, a HSI model of the carps is established, and the distribution of the carps HSI of the Dongliu channel in different periods is simulated and the influence of stage II waterway regulation works of the Dongliu channel on HSI of carps is preliminarily evaluated. The results show that stage II waterway regulation works of the Dongliu channel can increase the ideal area of Four Major Chinese Carps in spawning period, which is helpful for spawning and reproduction of the Carps; However, the influence in the growth period of Four Major Chinese Carps is slightly different due to the different periods，it is unfavorable to fish growth just after stage II waterway regulation works completion, but it will be beneficial to fish growth after a long period of stage II waterway regulation works completion. Therefore, the overall layout and scale design of the waterway regulation works should take full account of the impact of the project on HSI of the target fishes for producing the least impact on HSI of the target fishes, and even increasing HIS and area of the target fishes.