For launch vehicles using the liquid hydrogen and liquid oxygen propulsion system, the autogenous pressurization and thrust augmentation system is common used to provide high pressure propellant flow. However, it is very difficult to precisely measure the flow rate of the pressurized high-speed gaseous oxygen flow. A flowmeter for the oxygen flowrate measurement in the autogenous pressurization system is introduced and its design details are given in this paper. The integrated flowmeter consists of Venturi tube, pressure sensor, temperature sensor and signal conditioner. The proposed flowmeter is able to measure the oxygen flow of 0.2~1.5kg/s with the precision of 1.5% and the gaseous temperature range from 150K to 450K.The sturcture is specifically designed to improve the strength and reliability in the high shock environment up to 5000g. Series of simulation and experiment results are reported in detail. The simulation and experiment results reported in this paper show that the proposed flowmeter is reliable and safe for precisely measuring of the gaseous oxygen flows in autogenous pressurization systems.