The surface topography of workpiece plays an important role in the performance and service life of workpiece. Complex surface parts are widely used in shipbuilding, aerospace and other industries. At present, the study of milling surface topography is mainly on 3-axis milling. A prediction model of milling surface topography is proposed, which can obtain the machined workpiece surface topography and roughness directly from cutting parameters, cutter location file and workpiece surface geometry. The effects of cutting parameters on surface roughness is discussed. Different milling experimental conditions are set up to validate the proposed model. This method can be used to analyze the surface topography of milling, and further to optimize the cutting parameters to improve the surface quality.