Abstract: To address the challenges of traditional uniaxial compressive strength (UCS) testing for roof rock formations,we proposed an in-situ method that estimated UCS using drilling parameters. Focusing on the extrusion and crushing behavior of a PDC anchor bit in plastic soft rock,we derived a relationship between cutting force and UCS based on the mechanics of rock breaking by the cutting edge. An in-situ testing method for rock strength was proposed. Laboratory experiments were conducted on mortar samples of varying strengths using a custom-built drilling test device with constant drilling pressure,measuring drilling rate,torque,and rotation speed. Results indicate that torque is positively correlated with rock strength,cutting edge width,and cutting thickness. To account for differences between the dynamic drilling process and static analysis,an adjustment factor was introduced;this factor remains constant for the same drilling machine. The average relative error between UCS values calculated by the theoretical model and those measured experimentally is less than 13%,demonstrating the model’s validity.