OBJECTIV E To investigate the calculation method of drug market share in budget impact analysis （BIA）in order to provide new ideas for BIA research. METHODS In view of the situation that some drugs had multiple indications or the indications in the drug instructions were not clear enough and inconsistent with the indications in the reimbursement catalogue ， starting from the concept of “times per person ”，the parameters such as sample hospital and average treatment time per person for each time were introduced to develop a new market share calculation method. At the same time ，the calculation process was demonstrated by taking the treatment drugs for liver cirrhosis as an example. RESULTS & CONCLUSIONS Taking treatment drugs of liver cirrhosis as an example ，the calculation results of market share showed that the results of the two calculation methods were quite different. The market share calculated on the basis of “the number of people ”was mostly higher than that calculated on the basis of “times per person ”. Compared with the traditional calculation method based on “the number of people ”，the calculation method of market share based on “times per person ”could calculate the market share more accurately ，which could solve the problem that the traditional method didn ’t fully consider that most drugs had multiple indications ，the indications of drug instructions were not clear enough and inconsistent with the reimbursement catalogue ，resulting in inaccurate calculation of market share；at the same time ，this method could also be used to try to solve the problem that the total number of patients could not be obtained from epidemiological data based on the average treatment time per person of each time in the sample hospital. This method can be considered when the indications of the target drug are not clear enough or there are multiple indications ，or when the researchers collect clinical ，epidemiological and medical insurance data to estimate the number of target population ，the prediction results of market capacity do not conform to the theoretical logic or actual situation due to the lack of necessary data ，or when the target disease has the characteristics of repeated attacks and short course of disease.