OBJECTIVE：To construct a calculation method which can accurately reflect the medical insurance fund expenditure of intervention scheme for cross-year survival patients ，and to provide reference for the research of medical insurance budget impact analysis（BIA）. METHODS ：Based on survival data of cohort model ，taking the patients diagnosed in each cycle in each year as a cohort，the number of per capita survival cycle of cohort patients in each state in the study year was calculated ，i.e. the average survival time ；on this basis ，the total cost of patients in all cohorts in the study year was calculated according to the number of people in each cohort and the per capita cost each cycle in each state. Taking the intervention scheme of a cancer as an example ， the calculation was carried out by the established algorithm ，and the calculation results were compared with the results of several common algorithms ；at the same time ，the application suggestions were put forward for the expansion of the constructed algorithm in special cases. RESULTS & CONCLUSIONS ：Compared with the several common algorithms ，the calculation process of the constructed algorithm is more in line with the process of medical insurance fund expenditure related to drug intervention scheme in the real world ，and it can flexibly adapt to the calculation needs in a variety of special situations. This algorithm can more accurately calculate the medical insurance fund expenditure of a intervention scheme in a specific year ，and to a certain extent solve the problem of inaccurate prediction of medical insurance fund expenditure due to insufficient consideration of cross-year survival patients or simple and rough calculation process. It can provide a more accurate method choice for the research of medical insurance BIA in China.