The laser beam drift is one of the key factors that influence on the accuracy of laser measurement of straightness errors, and a novel method for straightness error measurement based on common-path compensation for the laser beam drift was proposed. The measurement principle and system configuration were given, influences of the laser beam drifts caused by different factors on straightness error measurement were analyzed，and a compensation model was established.After compensation,the results show that the variation of emission beam is reduced from 28.4 μm to 5.6 μm and from 21.6 μm to 5 μm in X direction and in Y direction, respectively,and the variation of beam drift due to temperature gradient is from 65.7 μm to 8.9 μm. Both experimental results and theoretical analysis show that the common-path compensation for the laser beam drift method can decrease greatly the influences of the laser beam drift on the straightness error measurement, and can enhance its measurement accuracy.