Various kinds of methods of entanglement detection and definitions of entanglement measurement in quantum systems were reviewed. For entanglement of two or more particles, some separability criterions were summarized. Their relationships with positive map and the relationships between themselves were also analyzed. Particularly, concentrations on entanglement witness are paid which is a special criterion involving its definition and construction methods. Further, its applications are also investigated from the viewpoint of experiment. Based on axiomatic hypothesis of entanglement measurement, the theoretical definitions of two-particle and multipartite entanglement, and their estimations in experiment were discussed. At last, various nonlinear separability criterions were analyzed.