Aircraft maintenance order is the main basis for military aircraft maintenance work. The orders specify all preventive maintenance tasks involved in aircraft basic level maintenance. With the accumulation of aircraft use and maintenance experience, the demand for optimization of maintenance task interval is becoming more and more obvious. Taking the service data as the analysis object and the system reliability as the measurement standard, this paper constructs the mathematical model of preventive maintenance task interval optimization analysis. Taking a maintenance task as an example, this paper analyzes its service data, and gives suggestions on maintenance interval optimization. The example has proved the feasibility of the mathematical model which can be used as a reference for military aircraft maintenance task interval optimization analysis.