Abstract: The multifocus image focus is discussed. Since light imaging system has a limited focus range,all other objects have blurry images to some different degrees besides the focused object,but we often want to acqurire a image on which all objects are clear. In order to get such a image, image fusion method can be applied and two multifocus image can be combined. The property of system function of multifocus imaging system is analyzed according to the circuit and system theory, and the conclusion is that the system function of the optical imaging system is a low pass filter.A multifocus images fusion method based on wavelet packet transform is presented according to the fusion perpose and the property of wavelet packet transform.Two practical multifocus images are fused with the fusion method and a satisfactory clear image is obtained. The experiment results show that the fusion method based on the wavelet packet transform can analyze both the low frequency and high frequency parts of the signal simultaneously at multifocus images.An image on which all objects are clear is provided.