The invention provides an engine jet 
pipe preparation method of a 
space launch vehicle. The preparation method comprises the steps that an engine jet 
pipe matrix and a housing are provided, wherein two protruding ribs arranged at intervals are at least included in the outer surface of the engine jet 
pipe matrix, and grooves are formed by the two protruding ribs and the engine jet pipe matrix in the parts between the two protruding ribs; the housing is matched to the outside of the engine jet pipe matrix, wherein the housing, close to the engine matrix, is in 
close contact with the protruding ribs; and on the surface, away from the protruding ribs, of the housing, 
laser produced by a 
laser generating device is enabled to move along the positions corresponding to protruding ribs, so that thehousing is fixed to the engine jet pipe matrix by 
welding to the protruding ribs, thus, a cooling passage for the flow of 
coolant liquid is formed by the grooves and the housing. According to the engine jet pipe preparation method of the 
space launch vehicle, the 
laser welding method is adopted, through directly 
welding the housing with the engine matrix in the outside of the engine jet pipe housing, the 
welding process can be greatly simplified, the welding cost can be reduced and the welding quality can be improved.