In order to achieve the multiple purposes of the highest CO² flooding recovery and the largest CO² storage in high water cut reservoirs，an objective function of collaborative CO² flooding and storage optimization for high water cut reservoirs based on economic net present value （NPV ） was established by considering CO² injection cost， CO² flooding and storage benefits. Combined with the reservoir numerical simulation method，we used simultaneous perturbation stochastic approximation （SPSA） to solve the objective function iteratively. Taking a high water cut reservoir in Shengli Oilfield as an example，the different injection timings of water transferring to CO² were set according to the different characteristics of water cut in the reservoir at different times. The optimization of water injection and CO² injection schemes was carried out， respectively， and the differences in production behavoir and NPV under the two injection methods were compared. The influence of gas injection timing on cumulative oil production and CO² storage was analyzed， and the optimal gas injection timing was determined. In addition， the effects of different gas injection prices and CO² storage subsidy schemes on their economic benefits were analyzed. The results show that the water cut should be lower than 0.97 during waterf transferring CO² injection to make the CO² flooding project profitable in high water cut reservoirs. The high project profit can be guaranteed as CO² is injected earlier when the CO² injection price is 1.2 yuan/m³， and the carbon subsidy is 0.114 yuan/m³.