Technical solution: An electric motor controller for controlling an AC motor in a car, connected between the vehicle controller and the AC motor. The electric motor controller comprises an auxiliary power module 10, a digital signal processor DSP20, an inverter 30, a CPLD module 40, a protection module 50, and a sensor module 60. Among them, an auxiliary power module 10 for providing power to the DSP is connected to the digital signal processor DSP; The data acquisition head in sensor module 60 is connected to the AC motor as the input end of sensor module 60, and the sampling signal is transmitted to DSP20 through the output end of sensor module 60; A protection module 50 for detecting voltage and current of AC motors, transmitting the obtained voltage and current detection signals to CPLD module 40; CPLD module 40 performs logical processing based on the received voltage and current detection signals, and uses the processed signals for fault indication and total fault signal transmission to DSP20. It also transmits the switch signal used for protection to control the opening and closing of inverter 30 to inverter 30; DSP20 receives user signals from the vehicle controller, instrument interface signals, and digital drive interface signals, receives total fault signals from CPLD module 40, samples signals from sensor module, and outputs total control signals to inverter 30; Receive sampling signals from sensor 60 and transmit them to the vehicle controller; Inverter 30 controls the AC motor based on the received space vector pulse width modulation signal. Among them, the DSP20 specifically includes: a vehicle communication module 21, an electric motor vector control module 22, a space voltage vector pulse width modulation module SVPWM23, an analog-to-digital conversion module 24, and a sensor signal processing module 25. Among them, the vehicle communication module 21 receives user signals, instrument interface signals, and digital drive interface signals from the vehicle controller, and transmits the received signals to the electric motor vector control module 22; Receive signals from sensor signal processing module 25 and transmit them to the vehicle controller; The analog-to-digital conversion module 24 receives a sampling signal from the sensor module 60, preprocesses the sampling signal and converts it into a digital signal, which is then transmitted to the sensor signal processing module 25; The two output terminals of the sensor signal processing module 25 are respectively connected to the vehicle communication module 21 and the motor vector control module 22; The motor vector control module 22 receives signals from the vehicle communication module 21 and the sensor signal processing module 25, and transmits them to SVPWM23; The input end of SVPWM23 is connected to the motor vector control module 22, and the output end is connected to the inverter 30. Among them, the protection module 50 includes an overvoltage protection module 51 and an overcurrent protection module 52. Among them, the overvoltage protection module 51 detects the voltage of the busbar in the circuit and transmits undervoltage or overcurrent signals to the CPLD module 40; The overcurrent protection module 52 detects the phase current of the AC motor and transmits the U phase peak valley and V phase peak valley signals to the CPLD module 40. Among them, the DSP20 is a TMS320F2803 series chip. Among them, the CPLD module 40 is an EMP3000 series chip