Abstract: The apparent friction coefficient has been widely used by international scholars as an indicator to quantify the high mobility of rock avalanches. However, due to it lacks physical meaning and can not reflect the energy variation of the sliding mass, the equivalent friction coefficient, as a quantitative indicator to quantify the variation of sliding mass center, is arising more and more scientific attention in recent years. Facing the difficulty in mass center acquisition and the complexity of calculating the equivalent friction coefficient, 34 non-obstruction rock avalanches were analyzed here with their equivalent coefficients being calculated based on high-resolution and high-precision digital elevation models and an effective method for reconstructing the pre- and post-avalanche terrains was proposed. Meanwhile, the quantitative relationship between the initial geometric parameters of the sliding mass and their kinematic parameters was discussed. The main conclusions are as follows: 1) The equivalent friction coefficient of non-obstruction rock avalanches mainly ranges from 0.24 to 0.38, slightly higher than their apparent friction coefficient, but significantly lower than the Coulomb friction coefficient of rock and soil masses, indicating that the movement of rock avalanches is low-energy-consuming. 2) Compared with the accumulation volume, the friction coefficients display a better relationship with the detached volume, indicating that the detached volume is more suitable in the prediction of avalanche mobility. 3) Compared with the apparent friction coefficient, the equivalent friction coefficient has a stronger correlation with the detached volume, suggesting that the equivalent friction coefficient is more reasonable in characterizing the "volume effect" of rock avalanches. 4) Compared with the whole horizontal runout of the mass and the runout of mass center, the friction coefficient has the strongest correlation with the excessive runout of avalanche mass and the weakest correlation with the whole horizontal runout. Through a systematic analysis on the quantitative relationships among the volume, friction coefficient, area, and runout of the non-obstruction rock avalanches, some results were reached here, hoping to provide scientific basis for the effective distance prediction of rock avalanches and serve disaster prevention and mitigation.