Objective: To study the changes of the expenses of laparoscopic cholecystectomy under the day surgery, and to analyze the effect of this mode on the expenses. Methods: Statistical test and inference is made on the expense structure and expense details of three groups of LC patients (day surgery group, over-night group pre-implementation and post-implementation of day surgery) in a sample Grade 3A general hospital from January 2017 to May 2022. Meanwhile, interrupted time series is used to analyze the net im- pact of day surgery on the expenses. Results: There is no statistical significant difference in the average expenses between these two over-night group before and after the implementation(P＞0.05), and the expenses of the day surgery group are significantly lower than that of these two over-night group before and after the implementation, which decrease by 3 946.89 yuan and 4 161.70 yuan, respec- tively. ITS also shows that the net effect of day surgery is to reduce the average total expenses by 48.63 yuan per month, among which the drug expenses decrease the most, and has no significant influence on the diagnosis expenses and treatment expenses. Conclu- sions: The day surgery plays a positive role, and the expenses related to the length of stay show a large decrease, but the expenses re- lated to the treatment process do not have a significant change.