To expand optical wavelet transform method into the digital signal processing domain,the optical implementation method of discrete wavelet transform algorithm(Mallat algorithm) for optical 4f system is proposed.Because amplitude-only Spatial Light Modulator(SLM) can only implement non-negative real function and CCD can only record light intensity,a design method for optical wavelet filters used in optical 4f system is presented.According to the sampling spacing,the two-dimension wavelet filters are constructed with one-dimension coefficients of wavelet filter in terms of tensor product method.Then the frequency domain wavelet filters in the form of non-negative real function are constructed with splitting,Fourier transform and normalization.Finally,the corresponding optical wavelet transform post-processing method is given.With this kind of optical wavelet filter and its corresponding post-processing method,the wavelet decomposition is implemented by optical 4f system,and wavelet reconstruction by numerical computation in Mallat algorithm.The simulation experimental results show that the input images can be reconstructed theoretically by proposed method with high precision,the average reconstructed PSNR is 54.27 dB,even under the condition of introducing the optical device quantization error.Also,the input images with good quality can be reconstructed by optical experiment in actual optical 4f system.The simulation analysis and optical experimental results verify proposed method.