Abstract: The existing shear stress correction formulas for direct shear test do not consider interface friction between shear box and soil sample caused by without gap between the two halves of shear box during shear for China direct shear apparatus. The soil-brass interface friction tests are carried out, and the friction coefficient of soil-brass interface is measured, which is 0.2.A shear stress correction formula for direct shear test considering interface friction and change of sample's cross-sectional area is proposed. Direct shear test results of peak and residual drained shear strengths from the literature are assessed by this formula. The conclusions are drawn as follows: 1) The shear stress after correction is greater than before correction. Relative error of shear stress increases with the increase of horizontal displacement and increases with the decrease of vertical pressure. 2) Initial density has a significant effect on the relative error of peak shear strength, but has little effect on the relative error of residual shear strength. 3) Relative errors of effective friction angle of peak and residual drained shear strengths under different initial density are within ±5%. Relative errors of effective cohesion of peak and residual shear strengths have larger changes with different initial density. 4) The effective friction angle and cohesion of peak and residual drained shear strengths after correction are all greater than that before correction, which means adopting the uncorrected shear strength parameters is conservative.