[Purposes] This work aims to predict rock mechanical porameters in advance rapidly and auurately. [Methods] By analyzing the force characteristics of the drill bit, a mathematical model is established to describe the machine-rock interaction during the drilling process using the principle of mechanical limit equilibrium. An analytical method of the primary rock strength parameter, which includes the internal friction angle, uniaxial compressive strength, and tensile strength is proposed based on digital drilling technology. To verify the reliability of this method, a self-developed high-precision digital drilling system is employed to predict the internal friction angles of four different types of rocks. Which are compared with the measured values obtained from laboratory tests. Through correlation analysis of rock strength, internal friction angle, and cutting strength ratio (the ratio of rock unconfined compressive strength to cutting strength), the rock strength is predicted and the results are verified. [Findings] The discrepancy of internal friction angle obtained by digital drilling technology and the standard test ranges from 1.0% to 3.5%. Moreover, the uniaxial compressive strength and tensile strength of the rock demonstrate linear and positive correlations with the cutting strength ratio. The error between the predicted rock strength and the measured values from standard tests is less than 20%. [Conclusions] The reliability of rock mechanical parameters predicted by digital drilling technology is confirmed, this method has certain application value in practical engineering.