The invention relates to an intersection merging assistant early warning system and method based on millimeter wave radar. The system comprises a signal transmitting module, a signal receiving module,a signal processing module and an information display module. The method comprises the steps that intermediate frequency signals are divided into two groups of frequency signals; FFT and OS-CFAR processes are carried out on each group of frequency signals, and distance and speed estimation is performed through phase processing; FFT processing is carried out on the other group of intermediate frequency signals, frequency point data corresponding to a main channel FFT result is extracted, interference phase comparison is carried out, angle information of a point trace is obtained, and orientation information of the point trace is obtained; condensation processing is carried out on several pieces of point trace information with similar position and speed values, and the condensed target is tracked and filtered. According to the intersection merging assistant early warning system and method, the millimeter wave radar is adopted to serve as an intersection vehicle information detection mode, real-time information display and tracking for vehicles is realized through transmitting microwaves to the region of interest, traffic information is provided for drivers through an information display screen, and thus a purpose of avoiding traffic accidents is achieved.