The sustainability of the employees' basic medical insurance pooling fund (hereinafter referred to as the pooling fund) and the corresponding financial responsibility depends on the the fund's income and expenditure, and are affected by many factors such as the number of insured people, the contribution base and the growth of medical expenses. The aging of the population in China leads to the increasing payment pressure of the pooling fund. How to ensure the sustainable operation of the pooling fund and reduce the financial burden? In this paper, the actuarial model is used to find that under the current pooling mode, the node where the pooling fund starts to show current deficit is 2029, the node where the cumulative deficit begins is 2040, and the cumulative financial responsibility is 10689.131 billion yuan by 2050. If the outpatient mutual aid reform is fully implemented in 2023, when the reimbursement ratio of outpatient expenses is 50%, the pooling fund will have a current deficit in 2041, and the node with a current deficit will be delayed for 12 years, and there will be no cumulative deficit by 2050. Increasing the reimbursement ratio of outpatient expenses will advance the point at which the fund begins to show current and cumulative deficits. When the reimbursement ratio of outpatient expenses is the same as that of hospitalization expenses (75.6%), the pooling fund will start to show a current deficit in 2037, and the current deficit node will be delayed for 8 years. The cumulative deficit will start to appear in 2049, the cumulative deficit node will be delayed for 9 years, and the cumulative financial responsibility will be 1594.767 billion yuan by 2050. It can be seen that the reform of outpatient mutual aid is conducive to the stable operation of the pooling fund in the short and medium term and reduce the financial pressure.