The financial status of the basic medical insurance fund for urban and rural residents (hereinafter referred to as the resident medical insurance fund) depends on the size of the fund's income and expenditure, and is affected by factors such as coverage, financing standards, and benefits. How do these factors affect the sustainable operation of the residents' medical insurance fund? In this paper, the actuarial model is used to find that if the coverage and benefits of 2020 remains unchanged, the resident medical insurance fund will have a cumulative deficit in 2036, which cannot achieve long-term sustainable operation, and the cumulative deficit by 2050 will be 9953.525 billion yuan, and there will be a large fund deficit. The expansion of coverage will affect the fund income and expenditure, but will not change the node where the fund has current deficit and cumulative deficit. Whether universal coverage will be achieved in 2035 or in 2050, the point at which the fund starts to run current and cumulative deficits is 2026 and 2036, respectively. To achieve universal medical insurance by 2050, the cumulative deficit will be 412.368 billion yuan more than the participation rate will remain unchanged. It can be seen that the expansion of coverage is not conducive to the sustainable operation of residents' medical insurance funds. When the cumulative deficit occurs in the baseline scenario, if only the individual contribution amount makes up the deficit, the individual contribution amount will increase to 3249.87 yuan in 2050, and the ratio between the government subsidy amount and the individual contribution amount is 0.89, and if the deficit is covered by government subsidies, the cumulative additional subsidies will reach 9953.525 billion yuan. If the outpatient insurance benefits are reduced to reduce the fund expenditure, even if the reimbursement ratio of outpatient expenses is reduced to 0, the resident medical insurance fund will still show a cumulative deficit in 2049. If the hospitalization insurance benefits are reduced to reduce the fund expenditure, when the actual reimbursement ratio of hospitalization expenses is reduced to 49.4% at least, the accumulated deficit of the medical insurance fund will not appear in 2050. If the outpatient and inpatient insurance benefits are reduced at the same time, the combination of the minimum reimbursement ratio of outpatient and inpatient expenses reducing to 41.1% and 51.1%, respectively, can prevent the cumulative deficit in 2050 and realize the long-term stable operation of the medical insurance fund.