Considering the case of dot gain, a color prediction model of FM halftone printed image based on Murray-Davies equation was studied. The microscopic structure and characteristics of FM halftone image was analyzed and a reflectance model for FM halftone image in ideal state was established. Taking into account the influence of light scattering, the relationship of reflection and transmission partially for dots and vacancy between dots was analyzed using the theory of light scattering. Based on the analysis above, a new prediction model based on expanded Murray-Davies equation for FM halftone printed image on microscopic level was developed.