Chinese word segmentation and Part-of-Speech (POS) tagging have been commonly considered as two separated tasks. In this paper, we present a system that performs Chinese word segmentation and POS tagging simultaneously. We train a segmenter and a tagger model separately based on linear-chain Conditional Random Fields (CRF), using lexical, morphological and semantic features. We propose an approximated joint decoding method by reranking the N-best segmenter output, based POS tagging information. Experimental results on SIGHAN Bakeoff dataset and Penn Chinese Treebank show that our reranking method significantly improve both segmentation and POS tagging accuracies. 1