EN-AC 48000 aluminum alloy is an important alloy in industries. Machining of this alloy is of vital importance due to built-up edge and tool wear. Three type of cutting tools including coated carbide (CD1810), uncoated carbide (H10), and polycrystalline diamond (CD10) have been used in this research In This Paper, the effect of machining parameters including lubricant emulsion percentage and tool material on surface roughness has been studied in machining process of EN-AC 48000 aluminum alloy. A L9 Taguchi standard orthogonal arrey has been applied as experimental design to investigate the effect of the factors and their interaction. Nine machining tests have been accomplished with three random repetitions, resulting in twenty seven experiments. Emulsion percentage of lubricant is selected in three levels including 3% , 5% and 10%. Statistical analysis has been employed to study the effect of factors and their interactions using ANOVA method. Moreover, optimal factors level has been presented through signal to noise ratio (S/N) analysis . Also, a regression model has been provided to predict the surface roughness. Finally, the result of the confirmation tests have been presented to verify the adequacy of the predictive model. In this research, surface quality was improved about more than 9% by using lubricant and statistical optimization method.