Abstract: An estimation method of the ship radiated noise level based on matching field processing (MFP) is proposed to decrease the measurement error caused by the propagation of the radiated noise in the complex underwater acoustic channel. Under the assumption that the ambient noise is temporally and spatially white Gaussian distributed, the location and the power spectrum response of the radiated noise source can be obtained while the ocean environment parameters are all known. A calculation formula of the power correction factor for the power response of the MFP at the location of the noise source is introduced, and the product of the power correction factor and the output power response of the MFP at the location of the radiated noise source is theoretically proved to be the minimum variance unbiased (MVU) estimation of the real source power. The processing steps of this method axe presented as follows: (1) the replica field vector can be calculated by appropriate acoustic field calculation model~ and the received source level (RSL) and the location of the measured ship can be obtained by MFP. (2) Utilizing the replica field vector at the location of the measured ship to replace the real channel transfer function to calculate the power correction factor. (3) The MVU estimation of the origin source level can be obtained by the product of the RSL and the power correction factor. Numerical simulations in a typical shallow water environment demonstrate the effectiveness of the proposed method. When the source to noise ratio satisfies a certain requirement, the difference between the source level estimated by proposed method and the origin source level is less than 1 dB.