The utilization of Al 1050/SiC particulate materials in many different engineering fields has undergone a tremendous increase. Accordingly, the need for accurate machining of this type of metal matrix composites has been increased enormously. In the present research, an attempt has been made to examine the effect of cutting parameters (cutting speed, depth of cut, feed rate) and two parameters of composite reinforcement; volume fraction and particle size on the machined part surface roughness through the investigated mathematical model developed by using the results gathered from a series of milling experiments. For this purpose, the experimental were reported for five of the maintained parameters. Twenty-five workpieces were fabricated to cover these investigations. A vertical milling machine was used in machining of Al 1050 / SiCp MMCs. The surface roughness (Ra) results were reported with different cutting parameters. The results of research indicated that ; the investigated procedure can be used to predict the surface roughness (Ra) for milling Al  1050 /SiCp MMCs, the experimental results and the predicted data by developed model indicate a good correlation, the surface roughness (Ra) decreases with the increase of cutting speed up to 140 rpm, but the surface roughness increases with the increase of ; depth of cut up to 1.5 mm, feed up to 1.25 mm/rev, volume fraction up to  25% and practical size up to 25µm.Also, the use of high cutting speed (140 rpm) , depth of cut 0.25mm,feed 0.4 mm/rev , volume fraction 5% and practical size 7.0 µm gives a good surface roughness (Ra) as compared with other values of the parameters used in this research.