Abstract: Tool sequences optimization（TSO） can largely promote the efficiency of pocket rough milling.As an important link of the TSO process,an improved method for generating feasible tool sequences（FTS） is proposed.The analysis of the current FTS generation method based on directed graph indicates the method constructs oversize solution space due to its approximately pure mathematical permutation and combination,which restricts the optimization performance.In order to improve the current method,based on analyzing the advantages and disadvantages generated in the process of tools combination,an analytical model for judging the validity of tool sequences is established.By importing this model to the current method,a large amount of the invalid tool sequences are eliminated from the solution space,thus the optimization performance is accordingly promoted.The implementation techniques,including the tool sequences validity analysis,of the new method are studied.The case study shows the obvious effect of the improved method in eliminating invalid tool sequences.