The accurate estimation of state of charge (SOC) for battery is an important content of electric vehicle battery management, and it is also significant for extension of battery lifetime and improvement of electric vehicle performance. A lot of research on SOC estimation methods is done by researchers all over the world, and kinds of estimation methods are proposed. In this paper, the definition of battery SOC and its main influencing factors are introduced, according to the characteristics of estimation methods for battery SOC, the SOC estimation methods are summarized and recommended based on offline and online methods, the characteristics and practical effects of each method are compared. In order to give reference to the further research about SOC estimation methods for power battery in future, two potential development directions of battery SOC estimation method are prospected, they are the nonlinear filtering method based on the cell model and the intelligent method with self-learning ability.