The invention discloses an estimating method for the initial value of the stage of charge of a high-accuracy lithium ion battery and belongs to the technical field of automobile power batteries. The estimating method comprises the following steps: firstly, according to a corresponding relation curve of the open-circuit voltage and an SOC (Stage of Charge) at different temperatures, estimating an open-circuit voltage stage of charge (SOCocv) through the lookup table; secondly, according to standing time of the battery, the current voltage platform of the battery and the battery pack temperature, obtaining a power-on initial stage of charge through the three-dimensional lookup table; finally, according to the self-discharging characteristic of the battery, correcting the initial stage of charge. Through the adoption of the method disclosed by the invention, an accumulated error caused by inaccuracy of the initial value estimated through an ampere-hour integral method and the estimation error of stage of charge caused by static current loss in the shutdown process are effectively reduced on the basis of factors of the characteristics of the open-circuit voltage at different temperatures, the standing time of the battery, the self-discharging characteristics of the battery and the like, and the higher accuracy is achieved. The method is suitable for SOC initial value estimation of a single battery, a module and a battery assembly.