The work aims to design a multi focus image fusion scheme with focus measurement and fuzzy logic based on three different focusing measurement and fuzzy inference systems, to keep clear source image information and effectively suppress block effect and ghost phenomenon in multi focus gray image fusion. Firstly, the Spatial Frequency (SF), the improved Sum-Modified Laplacian (SML) and Sum of Gradient (SOG) were respectively used to calculate the local focus feature of the input gray image in pixel neighborhood, and the pixel correlation was used to improve the contrast, thus getting three kinds of focusing measurements of SF, SML and SOG. Secondly, according to the intensity relationship between SF and SML, the focus tri-state map was established, which combined complementary focus information and performed morphological, median filtering and consistency checking to eliminate narrow gap and protuberance. Then, the fuzzy logic operator was introduced, the SF, SML and SOG of each pixel were taken as fuzzy inputs, and the fusion weights of each image were generated by fuzzy rules and defuzzer. At last, the final fused image was formed on the basis of the weight fusion performed by the focus weight. The experimental results showed that, compared with the current popular fusion schemes, for the gray image, the proposed algorithm had some advantages in fusion performance, and the fused image had better depth information, avoiding block effect and ghost phenomenon. The proposed algorithm has good fusion quality which can effectively improve the resolution of the gray image, and it has certain value in the field of image processing.