Large vocabulary continuous speech recognition (LVCSR) is the ultimate goal of speech recognition. When incorporated with other techniques such as language understanding and spoken dialogue management, a variety of speech-based intelligent applications and services are realized to enrich interaction between human and machine. This article gives readers a brief introduction to modules in weighted finite-state transducer (WFST) based LVCSR system, including acoustic feature extraction, acoustic model training algorithms, language model training algorithms, and decoder architecture. In addition, recent performance of Mandarin LVCSR systems in GALE project and some issues specific to Mandarin are addressed.