A shear strength dereferencing method for a coarse-grained soil direct shear test comprises the following steps: 1, obtaining a shear stress-shear displacement relation schema according to an actually-measured shear stress t/kPa and an actually-measured shear displacement s/mm; 2, obtaining a Dt/(Ds.tmax)-s relation curve through a formula of Dt/(Ds.tmax)-s; determining a 'grain breakage' starting point and a 'grain breakage' terminal on the Dt/(Ds.tmax)-s relation curve; 3, defining the 'grain breakage' starting point as the critical plastic shear strength and the 'grain breakage' terminal as the limit shear strength. Therefore, the shear strength of the coarse-grained soil direct shear test can be obtained through the steps. According to the invention, the critical plastic shear strength and the limit shear strength of the coarse-grained soil direct shear test can be accurately determined according to the 'grain breakage' starting point and the 'grain breakage' terminal on the Dt/(Ds.tmax)-s relation curve, so that the possibility that the conventional dereferencing method is influenced by human subjectivity can be reduced.