Abstract: Due to the hysteresis effect of lithium battery, the relationship between the open-circuit voltage and state of charge is complicated, so it is difficult to model and estimate the state of charge accurately. With lithium manganate battery monomer as the research object, through the experiment based on analyzing the hysteresis characteristics, the simplified open-circuit voltage hysteresis model was put forward, the hysteresis factor was constructed according to the size of the state of charge accumulation between the open-circuit voltage difference in the hysteresis main loop, and corrected the relationship between the open-circuit voltage and the state of charge to improve the accuracy of the battery equivalent circuit model; Secondly, aiming at the abnormal disturbance of measurement noise, the change of model and the deviation of the initial value of the state of charge, the method of phased transformation to measure covariance and constructing adaptive factor was used to improve the unscented Kalman filter algorithm to balance the convergence speed and estimation accuracy of the state of charge. The experimental results show that the dynamic and static characteristics of the lithium battery are accurately described by the model, and the performance of the proposed adaptive unscented Kalman filter algorithm to estimate the state of charge is greatly improved.