The invention relates to a fall bar brake mechanism for a trailer and relates to the technical field of special vehicles. According to the fall bar brake mechanism for the trailer, a draw bar assembly, a base assembly and a fall bar brake assembly are mounted, so that the fall bar brake function is realized during manual traction braking or speed-reducing, the excessively fast speed is avoided, and the potential safety hazard is eliminated; at the same time, a draw bar auxiliary spring self-balancing draw bar assembly dead weight is mounted, so that manual operation is facilitated, and time and labor are saved.