State of health (SOH) is an important indicator of good battery performanceNew energy vehicle. Aiming at the target requirement of accurately estimating the health status of 18650 lithium battery, based on the mathematical model of lithium battery cell, the equivalent circuit model is used to analyze the factors affecting the health status of lithium battery, and the universal nonlinear battery equivalent circuit model is adopted. Gneral nonlinear model (GNL) and extended Kalman filter algorithm, the SOH estimation model of lithium battery was built in AMEsim simulation environment, and the charge and discharge cycle experiment of 18650 lithium battery was carried out. The collected data set was imported into the data module of AMEsim estimation model. The simulation results show that the SOH estimation error is less than 8%, and the established lithium battery SOH estimation model meets the target demand for High estimation accuracy and fast response.