In XML databases, materializing queries and their results into views in a semantic cache can improve the performance of query evaluation by reducing computational complexity and I/O cost. Although there are a number of proposals of semantic cache for XML queries, the issues of fast cache lookup and compensation query construction could be further studied. In this paper, based on sequential XPath queries, we propose fastCLU, a fast Cache LookUp algorithm and effiCQ, an efficient Compensation Query constructing algorithm to solve these two problems. Experimental results show that our algorithms outperform previous algorithms and can achieve good performance of query evaluation. Categories and Subject Descriptors H.2.4 [Systems] Subjects: Query processing General Terms: Algorithms, Performance, Languages