In order to meet the demand of coma measurement accuracy of lithographic tool projection lens, a novel method for measuring coma based on fine overlay error metrology marks is proposed. The impact of coma on the aerial image of the fine overlay metrology marks is analyzed and the principle of the method is described in detail. The sensitivity coefficients of overlay error relative to coma are obtained by the simulation software PROLITH under different numerical aperture and partial coherent factor. The simulation results show that with the conventional illumination condition, the ranges of sensitivity coefficients Kz7 and Kz14 are increased by 27.5% and 34.3% respectively, 20.4% and 22.1% for annular illumination. Compared with the widely used projection lens coma measurement method TAMIS, the accuracy of coma measurement is increased by 20%.