This paper deals with visualization of in-cylinder air motion during the scavenging process of a model two-stroke engine with poppet valves in the cylinder head. The combustion characteristic in two-stroke engine are very influenced with fresh gas concentration brought out scavenging gas flow. Therefore, the laser seat method was used to visualize the tracer in in-cylinder flow gas. In this experiment, shrouds were fixed to scavenging valves of the model engine to prevent short-circuit loss of scavenging gas. The flow characteristic were compared with it in cased of scavenging valves without shroud. As a result, the short-circuit loss was prevented by the shroud, and good scavenging flow of U type was got.