This paper presents an experimental study in high speed milling of SiCp/Al composites. Machining tests were carried out on a high speed milling machine by using chemical vapour deposition (CVD) diamond coated tools. The surface micro-topography was tested by the OLS3000 Confocal Laser Scanning Microscope. The Gaussian filtering method and the least square fitting method were used to treat the measured results. Two methods are compared according to the effect on keeping important original surface’s character. The results showed that the least square fitting method is suitable due to its good accordance to the original surface’s character.