Abstract: The present invention relates to a small four-stroke gasoline engine with oil mist lubrication. The lubrication oil way of the engine includes a crankshaft chamber B, a camshaft chamber C, an upper rocker arm chamber D and a condensation chamber E. The camshaft chamber C communicates with the upper rocker arm chamber D via a tappet cavity 13. The upper rocker arm chamber D communicates with the condensation chamber E. An oil mist chamber A is surrounded by an upper case body 3 and a lower case body 4 at the side of the crankshaft chamber B, the bottom of the oil mist chamber A communicates with the crankshaft chamber B. An oilsplash impeller 2 is fixed on a crankshaft, which extends into the oil mist chamber A. An oil way 12 is provided on the upper case body 3 between the oil mist chamber A and the camshaft chamber C. An oil return way 15 is provided on a cylinder head assembly 5. An oil return way 14 is provided on the upper case body 3.