Accurate estimation of SOC plays an important role in preventing excessive charge and discharge of lithium batteries, improving energy utilization rate of lithium batteries and ensuring safe and stable operation of battery management system. In this paper, a SOC estimation method based on multi-innovation identification theory is proposed for ternary lithium batteries. Adopting forgetting factor multi-innovation least square method for model parameter online identification by building a second order RC equivalent circuit model, multi-information unscented Kalman Filter algorithm was used to estimate the SOC of lithium batteries. Through Verified by UDDS experiment and were compared with EKF, UKF and MIUKF algorithm, the results indicate that FFMILS-MIUKF algorithm to estimate the error of the SOC control at around 1.08%, which has high accuracy and fast convergence.