The invention provides a lubricating oil separating device of a two-
stroke gasoline engine. The lubricating oil separating device comprises a
crankshaft box body, a
crankshaft, a
piston, an air cylinder, an air cylinder cover, an air inlet, an air ventilating hole, an air outlet and an air
scavenging duct, wherein the
crankshaft is mounted and arranged in the crankshaft box body, the
piston is positioned at the upper part of the crankshaft box body, the air cylinder cover covers the air cylinder, the air inlet, the air ventilating hole and the air outlet are formed in the air cylinder, the air
scavenging duct is formed in the air cylinder and connected with the crankshaft box body in a penetrating through manner, and a filter for filtering lubricating oil in flammable
mixed gas is mounted and arranged at a position of the air
scavenging duct between the air inlet and the air ventilating hole; the filter comprises S-shaped filtering screens, and the filtering screens can be multilayer. When the flammable
mixed gas flows through the filter, lubricating oil particles adhere to the filtering screens of the filter, so that the lubricating oil particles in the flammable
mixed gas are filtered, and the flammable mixed gas entering a burning chamber contains a mixture of
gasoline and air and little or zero lubricating oil; through the adoption of the lubricating oil separating device disclosed by the invention, the
gasoline can be fully burnt, and the problems of high emission and heavy
pollution because engine oil is burnt are solved.