In this paper, computational non-steady gas flow process simulating of intake system of Model SD2100 diesel engine have been made by using the characteristic method. In the meantime, intake air pressure waves in the engine intake pipe under different engine rotative speeds have been measured on the engine test rig with an inverted drive, and exploratory investigation conducted into the influence of intake pipe length, design of pipe branch, air fitter and other factors on the charging efficiency and intake air pressure wave. The computed results agree mainly with the measured data.Because of having used the design of two-branch short pipes equal-length in intake system of SD2100 diesel engine, the interaction phenomenon of intake air pressure waves of two cylinders each other is found out both in test and computation, thereby, the intake air chargings into two cylinders are unequal. Also, it is shown in computed results, there is the reversal of intake air flow in the late intake process of this engine. By simulating computation, proposals for improving the intake system of a two-cylinder diesel engine have been also offered.