The invention discloses a gasoline engine pressure lubrication system and a gasoline engine thereof, comprising an oil pump casing and an oil pump cover plate matched with the oil pump casing, the oil pump casing includes a rotor mounting seat, a filter screen mounting Groove and cover plate installation column, the oil pump housing and crankcase cover are integrated, the filter screen installation groove is arranged between the oil inlet cavity and the oil inlet hole of the oil pump housing, and the cover plate installation column is set On the outer wall of the rotor mounting seat; the gasoline engine pressure lubrication system and gasoline engine of the present invention, the oil pump housing is integrated on the crankcase, the crankcase is also used as the oil pump housing, and the oil pump housing is provided with a filter installation groove , so not only can the space for the oil pump and oil filter be omitted, but also the cooperation between the oil pump and the oil filter can be better, the number of parts of the gasoline engine can be reduced, the layout of the lubrication system can be optimized, and the complexity of the assembly process can be reduced at the same time. The cost of production and assembly is reduced, and the requirements of gasoline engines, especially general-purpose gasoline engines, are met.