Collapse always frequently occurs during the construction of tunnels due to the unfavorable geological conditions or other factors such as the excavation method, causing casualties, equipment damage, time delay or other adverse consequences. However, the current qualitative assessment method cannot satisfy the needs of project risk management.Hence, a novel quantitative assessment model of collapse risk is developed. Considering the variability of physical and mechanical parameters of surrounding rock, the probability of collapse is obtained by the Monte-Carlo method combined with the numerical method.The relevant zone of collapse is predicted by Protodyakonov's theory.With the predicted probability and zone of collapse, the risk of casualties, time delay and economic loss is analyzed quantitatively via introduction of spatiotemporal distribution index and vulnerability index.The quantitative assessment of collapse risk is realized by quantifiable risk acceptance criterion based on the way of ALARP principle and F-N curve.Finally, validated by engineering case history, the operability and applicability of the developed risk quantitative assessment model is illustrated.