Abstract: The main noise sources (boundary layer noise and propeller noise) of a turboprop aircraft in cruise status are calculated and verified respectively. VA-One software is used to calculate the noise of the boundary layer at different positions of the fuselage, and semi-empirical formula is used to calculate the near-field noise of the propeller. The calculated results of the two noise sources are compared with the measured results of the external surface noise of the turboprop aircraft. The results show that the results of simulated and theoretical calculations are in good agreement with the measured results, which verifies the correctness of the algorithm. The algorithm can be used to predict the noise load on the outer surface of turboprop aircraft and the noise in the cabin.