Abstract: Rock avalanche dynamics are always research hotspots and frontier issues in the field of geological engineering worldwide. Movement distance is crucial for determining threat objects and influence ranges in the field of geological disaster prevention. This study is based on the work-energy principle,assuming the landslide is well-distributed,disintegrated,and has a definite frictional coefficient. The work done by frictional force during the movement of the rock avalanche is calculated through calculus,and a formula for the movement distance after landslide instability is derived. The formula is related to four parameters: the height of the center of gravity of the landslide(H),disintegration coefficient(λ),slope angle(α),and angle of internal friction(φ). Two special cases of λ=0 and λ=1 are researched in the study. If λ=0,the formula for the movement distance is consistent with previous research results. The discriminant formula λ=1 is obtained,which is consistent with the discriminant formula of non-cohesive slope limit equilibrium state(slope angle equals natural resting angle). We chose 12 landslides from history and measured the disintegration coefficient(λ)based on geological cross-sections. Using Origin software,we fitted the disintegration coefficient(λ) and the ratio of the height difference of the landslides(ΔH)to the height of the center of gravity of the landslides(H₁). The results show that λ and ΔH/H₁ form an exponential function. Comparing the calculated distances with the measured distances of the 12 landslides,the average error is within 5%. Finally,taking the Gewo landslide in Sichuan Province as an example,we predicted the movement distance after instability using the formula derived in this study.