The invention discloses a fall prevention safety device for climbing personnel on a tower crane. The fall prevention safety device comprises a braided rope; the braided rope is wound on a ratchet wheel clockwise; the ratchet wheel is fixed on a shell through a ratchet wheel shaft; a pawl is arranged at the lower end of the ratchet wheel; the ratchet wheel shaft is connected with an output shaft ofa motor; a protection ring is arranged at the lower end of the shell; the braided rope penetrates out of the shell through the protection ring; a hook is arranged at the tail end of the braided rope;a guide wheel is movably arranged at the lower end of the shell; a speed sensor is arranged on the guide wheel; and rope break protection devices are arranged at the lower end of the guide wheel at intervals. The fall prevention safety device is convenient to use and ingenious in design, when the person is in danger and quickly falls down, the braided rope is locked by the fall prevention safetydevice, and meanwhile, the fall prevention safety device has a rope break protection function, so that the effect of protecting the safety of the person is achieved.