Most cells contain various transport vesicles that target to different destinations. The underlying molecular mechanisms are highly conserved in evolution. Sec1/Munc-18 (SM) proteins play an important role on regulating vesicle transport by interacting with soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) at each vesicle fusion sites. SM proteins interact with syntaxin, an important component in SNARE complex, to regulate the assembly of SNARE complex, and promote overall membrane fusion process together with SNARE complex. This review summaries new research progresses of structure and function of SM protein.