The rise of web services and service composition in recent years makes it necessary to pay special attentions to their robustness and integrity. One of the most ideal solutions is using testing technology, we are interested in checking whether the process satisfies a given temporal safety property, the cost of dynamic testing for distributed and heterogeneous applications is huge, so forward a static analysis technology applied in the BPEL service composition. Defect-based analysis is a suitable technique to measure the adequacy of test results which can detect the defects pulled in by the developers unintentionally. False positive rate and false negative rate are key evaluation criteria of static defect detecting, so in order to improve the accuracy of detection, the algorithm proposed in this paper for defects analysis involving the semantic analysis, i.e., dead path elimination (DPE). By using the abstract domain of variables in the expression of condition on link, we can identify whether it is the start of DPE or not. The whole paper takes the application of uninitialized variable detection to illustrate the effective of this method.