In recent years, the rapidly evolving quantum computing has become the focus of attention. However, quantum hardware suffers from scarcity and noise, which makes the study of quantum algorithms and the verification of quantum chips rely on quantum simulators running on classical computers. In this study, the main simulation methods used by different quantum simulators are discussed, and various optimizations of mainstream full-amplitude state vector simulators and tensor network-based quantum simulators are explored. Finally, the current status and future directions of quantum simulators are summarized.