Taking account of insufficiency of PrefixSpan algorithm, which is widely applied to data mining, this paper trys to optimize the algorithm by reducing frequency of exchanging between the memory and the external memory in the Prefix part, and reducing the size of the projection database by discarding the non-frequent items which created in the process of sequence patterns mining. The result of test demonstrates that the operating efficiency is enhanced more than 35%. The conclusion comes to shows that the improved algorithm is applicable to the Web Mining.