The invention discloses a charging fault diagnosis and safety detection system and method of an electric vehicle. The system comprises a BMS, a CAN wire, a VCU, a vehicle charger, a DC charging pile,an AC charging pile, a battery, a vehicle charging interface, a charging interface, a charging gun and a charging fault diagnosis and safety detection system, and the charging fault diagnosis and safety detection system comprises a signal acquisition unit, a national standard memory, a processing unit, a human-machine interaction interface and a relay. The method includes steps: the charging faultdiagnosis and safety detection system is externally connected between the vehicle charging interface and the charging interface of the charging gun, the connection to an electric vehicle charging system is realized through the CAN wire, and through collection of message information, acquired by the VCU, of the BMS and communication messages of the DC charging pile and the AC charging pile and comparison with an electric vehicle charging national standard, the reason of charging failure is determined, and charging is finished after occurrence of problems of overcurrent and overvoltage of charging. According to the system and the method, the charging detection efficiency and the charging security of electric vehicles can be greatly improved.