Abstract: In order to mine frequent episodes from an event sequence efficiently, an algorithm based on generalized suffix-tree was proposed to discover and store frequent episodes, which uses the concept of generalized suffix and contains only frequent episodes' nodes. The occurrence list of frequent episodes was used layer-upon-layer to improve the efficiency of the tree. The algorithm make full use of the order character of an event sequence and may discover the variety of frequent episodes. Experimental results show that the proposed algorithm is superior in runtime to Apriori-like frequent episodes mining algorithm.