Abstract: The shear strength characteristics of common limestone in engineering under different weathering degrees were seldom examined, and there is no mathematical model for rapid evaluation of the shear strength of limestone, which cannot meet the needs of prevention and control of a large number of limestone engineering disasters. In order to explore the influence of weathering degree on the shear strength characteristics of limestone, the fresh limestone samples are selected in the test. The rock samples with different weathering degrees are prepared by indoor weathering simulation test. The indoor rock strength shear test is carried out to explore the variation law of the shear stress-shear displacement curve of limestone and the deterioration law of shear strength and its parameters. The quantitative relationship between the weathering degree and shear strength is revealed by establishing the shear strength estimation model of limestone under weathering degree. The test results show that with the increasing weathering degree, the shear strength and residual shear strength of limestone show a decreasing trend, but the residual shear strength is worse than the shear strength, and the deterioration rate is faster. With the increasing weathering degree, the cohesion c and internal friction angle φ of limestone are getting smaller and smaller, and the deterioration trend is similar. Using the wave velocity ratio to quantify the weathering degree, the shear strength estimation model of limestone under weathering is established. The shear strength characteristics of rock can be quickly evaluated by simply measuring and calculating the wave velocity ratio of rock. The research results can provide a more simple and feasible method for evaluating the shear strength characteristics of limestone engineering.