An only-one correlation-peak joint transform correlator based on Mach-Zehnder interferometer is presented aiming at the shortcomings in the energy dispersion of correlation peak and of Classic Joint Transform Correlator(CJTC) the input image size and relative position to be restricted. The image input of proposed method has no relative displacement between input images by Mach-Zehnder interferometer, and realizes a high intensity overlap correlation-peak in the center of detector, so that the contradiction between the input image size and relative position with the transform lens aperture and detector reception area is relaxed. Moreover,zero-order autocorrelation peak is eliminated and diffraction efficiency is enhanced by power spectrum subtraction. The theoretical analysis and experimental results show that proposed method can offer a high intensity correlation-peak and its anti-noise ability is six times that of CJTC,which enhances the recognition ability of the system. Also,this method makes good use of the space bandwidth and reduces the system costs,so that it is suitable for large size image recognition and weak signal detection in noisy environment.