Based on relation equation of total pressure and static pressure, for better measuring Ma number, an improved algorithm of Mach number was proposed to measure Mach number. The algorithm made a Taylor expansion to Mach number measurement formulation, taking second order approximation, and introduced a correction factor which associated with Ma. Specific calculation steps were given. The simulation results show that it can satisfy the system requirements in precision and in real-time. It has a certain practicality and spreading value.