In view of the problems of heavy gas cloud and high risk of inflammability and explosion in oxygen/methane emission in the ground test of liquid oxygen/methane, liquid oxygen/kerosene and other rocket engines, a safe emission device was designed.The lower part of the general structure is collection box, and the upper part is evacuation tube.Using the method of function drived design and stress checking size, the structure design of several key parts of the emission device, such as collecting box, emptying tube and fixing bracket, were carried out.The design results were as follows: the collection box was a steel plate structure with angle steel frame welded inside.The section stress of the steel plate was 0.4 MPa, much lower than the allowable stress.The manhole was sealed by low-temperature rubber.The lower part of the evacuation tube was a flowered tube structure, which was inserted into the collection box and connected with it, and the middle part was welded to discharge nozzle.The average wind force in the suburbs of Xi'an was 111.2 N/m, and the maximum bending normal stress caused by it was 1.45 MPa, and the shear stress was 0.01 MPa, both of which had high safety factors.The stress amplitude of the bolt with fixed support was 2.1 MPa, lower than the allowable value of 9.7 MPa.The working process of the emission device was simulated by the numerical analysis tool.The analysis results were as follows: the maximum pressure in the collection box was 0.107 MPa, the maximum impact load at the discharge interface was 0.72 MPa, and the average outlet flow rate was 45 m/s, all of which met the requirements of strength and safe discharge.The emission device had been made and applied in relevant tests successfully for many times.The test results showed that the design method was feasible and the structure was reliable, realizing the expected function, which ensured the safe discharge of flammable and explosive media, such as oxygen and methane.