With the development of aerospace, biomedical and chemical industries, titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe (TC18) is becoming widespread used. TC18 has even better mechanical property than Ti-6Al-4V (TC4). For better cutting TC18, simulation model was set up. PVD and CVD coated carbide inserts were used to machine titanium alloy TC18. The cutting forces were measured. Milling model was set up for the extraction of the cutting force coefficients and chip flow angle. Results were compared. All the coefficients of CVD coated carbide insert were found to be larger than those of PVD coated carbide insert. The model was proved to be reasonable after validation.