Abstract: For the quality diagnosis of electron beam in range from 5 mA to 60 mA of a high-voltage electron beam welding machine,a CPLD(Complex Programmable Logic Device)-based control system of electron beam high-speed scanning was established by means of analyzing the principle of electron beam scanning in the electromagnetic deflection coils. The control system consists of industrial PC,CPLD chip,DAC(Digital to Analog Convertor),low pass filter circuits,optical isolation circuits, power amplifiers,electromagnetic deflection coil and external circuits of CPLD. The system controls the special phase relationship between the two waveform and the trigger and sampling frequency of the acquisition card. The scanning frequency can be adjusted within the range 0~15.6 kHz. The amplified power is the constant current mode and its maximum output current is 5 A. The signal parameters can be adjusted to change the scanning path of electron beam without changing any hardware circuit,so it is highly flexible.