Cutting force is a very important factor in machining processes for predicting chatter, surface roughness and machining efficiency. For a given cutter, cutting force is determined by cutting force coefficients and uncut chip thickness. Once a new cutter is adopted, repeated experiments are carried out to calibrate its cutting force coefficients. To reduce the high cost and longtime experiments, theoretical analysis of the effect of cutter parameters on cutting force is required. In current literatures, some cutter parameters, such as helix angle and pitch angle, have been studied to explore their effects on cutting force. However, there is little research about the effect of teeth number on the cutting force. To fill up this gap, the effect of teeth number on cutting force is studied in the paper. Firstly, it is derived and experimentally verified that the cutting force coefficients are unchanged for cutters with different teeth number but the same teeth parameters, e.g., rake angle, shear angle, etc. Secondly, by matching the measured cutting force point with the cutter rotation angle, the cutting force coefficients can be calibrated by only one experiment when we assume that the material of the cutter is the same. Therefore, the cutting forces generated by cutters with different teeth numbers can be predicted based on only one experiment. Thirdly, from the various comparisons, it is concluded that cutter with 2 teeth number is suggested for side milling and cutter with 3 teeth number is suggested for slotting when surface roughness is considered. The cutter with 5 teeth number is suggested when only the machining efficiency is concerned. Finally, various experiments are carried out to verify the proposed study in milling of titanium alloy Ti6Al4V (TC4), and the comparison results show a good agreement.