Abstract: Aiming at solving the supports dumping accidents in deep inclined fully mechanized caving face,the fault-tree model is established,combining the mechanism and influence factors of hydraulic supports instability.Under the circumstance that the probability of basic events is not clear,the article determines the fuzzy probability through the fuzzy theory,works out their importance by using the median method,and then puts forward the quantitative analysis method of supports dumping accidents in deep inclined fully mechanized caving face which is based on fuzzy fault-tree analysis.To set the 2313 fully mechanized caving face of one coal mine as an example,the paper builds the fault-tree model,calculates the fuzzy probability of basic events and the minimum cut sets.Through the importance degree analysis the article determines the main influence factors of supports dumping accidents in this fully mechanized caving face and then raises some well-targeted technical measures to protect the supports from dumping which ensure the stability of the supports in deep inclined fully mechanized caving face with the average inclination of 36°,maximum inclination of 51°.