Abstract: The noise from intake system of diesel engine is the most important noise source of a top-grade commercial vehicle, especially its interference inside the vehicle. Based on the theory of pipeline acoustics and flow resistance analysis, an approach named non-source method was proposed to simulate the noise from diesel engine so as to solve the problem that the acoustic simulation of intake system is so hard to carry out, i.e. no way will the geometrical/physical parameters be obtained though they are necessary to the simulation model of an engine. With the non-source method applied to the solution of such a problem, the computer simulation can be done without a relevant simulation model of noise from intake system. Then, both the noise and power loss of the engine can be predicted to provide a reference for the rapid and accurate acoustic optimization of engine's intake system.