Abstract: The study on time-domain separation method of noise source is very important for a turbo gasoline direct injection（TGDI） engine to optimize combustion noise,mechanical noise and improve the sound quality. According to the transmission characteristics between the radiated noise of the engine and the excitation sources such as cylinder pressure and load,the engine noise was separated and defined as combustion noise,load-dependent noise and residual mechanical noise. Based on the principal component regression analysis and the convolution theory,a time-domain separation method of engine noise source was proposed,and the time-domain separation model of TGDI engine noise sources was established. The coherence between cylinder pressure,load and noise was used to verify the correctness of the model. The separation of TGDI engine noise sources was carried out to obtain timedomain noise signals such as combustion noise,load-dependent noise and residual mechanical noise. The consistency between the measured and calculated value of residual mechanical noise was verified by the towing test method. The accuracy of the separation results was verified. The frequency spectrum analysis of three kinds of timedomain noise sources was carried out to determine the time-frequency domain distribution of the three kinds of noise source.