The Institute of Space and Astronautical Science has conducted the stage firing tests of the LH_2/LOX propulsion system at the final step of verification test on the LH_2/LOX propulsion system which has been developed in ISAS since 1976. Stage firing tests were performed with the battle-ship type of tank system and the 7-ton thrust level engine for the first time and then with the 10-ton thrust level one. The performance of these engines had been already verified in 1980 and 1981 respectively. From October in 1981 through April in 1982,eight stage firing tests have been carried out and the stage performance characteristics have been verified in the self-sustained operation. The 7-ton thrust level engine worked well within the range between 84.5 and 118% of its rated power and the 10-ton thrust level one within the range between 86 and 113%. And also both the startup and shut-down sequence including the chill-down operation of engine system have been examine and established. The PU (Propellant Utilization) control have been tried in the five test runs with good results.