Computational methods such as finite element simulation have been utilized in analyses of machining process for several decades. With the advance of the computing power, its applications can be further extended. In micro-machining, finite element simulation has been used for predicting cutting forces, minimal chip thickness, temperatures, and tool wear. The accuracy of results and time consumed are highly dependent upon the assumptions which govern that problem. This study shows a comparison of employing two different material assumptions in finite element simulation of micro-end milling titanium alloy Ti-6Al-4V. The same simulation was conducted by using the elasto-viscoplastic and the viscoplastic material assumptions. The results have shown that the material assumption has a major effect on the mechanism of chip formation and heat generation but it only has a minor effect on the cutting force and tool wear prediction. In terms of computational time, it was found that the viscoplastic model can reduce simulation time up to 8 times that of required for elasto-viscoplastic model.