Abstract: A waste gas treatment system is designed, to be used for treating the hydrazine and the ammonia gas in the tail gas from a certain type of engine during the ground test, and the remained gas is discharged into the atmosphere. Seven common methods for the treatment of the decomposition hydrazine waste gas are introduced in this paper. A method of spraying waste gas using treatment liquid is adopted after comparison. Technical parameters that the system actually has achieved include:the no-load operation flow of 944 Nm³/h; the gases from the engine ground test and after the system operation include hydrazine <0.0012mg/m³ and ammonia 0.0326-0.057 mg/m³ (factory boundary values, total 4 spots detected). The test result is much better than the value of the relevant national standard requirements. Dozens of engine ground test results have shown that the system can meet the user's requirements, with easy operation, reliable running, and almost no need of maintenance.