The invention discloses an approach electric safety early warning device for a construction machinery, which, in the structure, comprises an electromagnetic radiation measurement device, a camera device, an analog-to-digital converter, ultrasonic radars, a bottom plate, data input and output connectors, a USB interface, a spring movable supporting foot, a start button, a host, a display screen, asingle chip microcomputer controller, an alarm and a data line, wherein the ultrasonic radars transmit and receive ultrasonic signals through a vibration coil and a piezoelectric ceramic vibrator, thesignals are inputted to the single chip microcomputer controller of the host, the alarm carries out sound-light alarming when a boom approaches an obstacle for a certain distance during an operationprocess, the camera device is matched for use to intuitively inform a driver of the obstacle condition around the boom in an image mode, troubles caused by blind area visiting in front and back when the driver lifts the boom are relieved, the driver is helped to eliminate defects of visual field dead angles and blurred vision, the electromagnetic radiation measurement device can measure the electromagnetic radiation value in the area, and the alarm gives an alarm when the boom approaches a high-voltage area.