Abstract: Based on the tunable diode laser absorption spectroscopy(TDLAS) technique, temperature, concentration, velocity and mass flux of the supersonic flows were measured in isolator of a direct-connected scramjet. Two H2O absorption transitions 7 185.597 cm-1 and 7 454.445 cm-1 were adopted by using direct-absorption and Time Division Multiplexing strategy. The measurement results show the static temperature is of 899 K and the H2O concentration is of 20.7% calculating from the absorption area. A cross-beam configuration with angles of 60 along the flows was used to measure the axial velocity. Combined with the pressure sensor on the wall and the measured velocity of 1 205 m/s, the mass flux of the flow is of 1 500.49 g/s with deviation of 5.23%. The TDLAS measured system can be used for in-situ measurements of multiple parameters of supersonic flows.