With the large-scale development of electric vehicles in China, fault monitoring and early warning of electric vehicles during the charging process have received attention. This paper proposes a method for monitoring and early warning of electric vehicle charging faults based on a battery model. Through online estimation of the state of charge of the power battery model and battery electromotive force, parameters such as battery state of charge, voltage, and temperature can be adjusted in real time to simulate the charging response of the power battery, and can simulate power batteries of different types, specifications, and parameters. During the charging process, CAN bus monitoring technology is used to receive and analyze the charging information of the charger and battery. The charging response information simulated by the battery model is compared with the battery charging state information, and the charging state information of the charger is compared with the battery charging demand information to determine whether the charging process is normal. When it is judged that there is an abnormal charging or fault, a fault early warning signal is sent in good time. This method can identify more than 10 types of fault, including the failure of the BMS function. The actual charging data is used to verify the feasibility of the fault monitoring method under normal and abnormal charging conditions. This work is supported by the Science and Technology of State Grid Corporation of China “Research on Key Technologies and Operation Maintenance Service System of EV Charging/Discharging Fault Intelligent Diagnosis and Safety Warning” (No. 5418-201918159A-0-0-00).