The invention discloses a bridge inspection vehicle frequency conversion control system. The bridge inspection vehicle frequency conversion control system comprises a frequency converter, a PID controller, an image acquisition module and a speed prejudgment module; the frequency converter is in communication connection with a motor and is used for conducting frequency conversion control on the motor; the PID controller is in communication connection with the frequency converter and a speed sensor and is used for conducting closed-loop control on output signals of the frequency converter according to detection signals of the speed sensor; the image acquisition module is used for acquiring image information in the advancing direction of a bridge inspection vehicle; and the speed prejudgment module is in communication connection with the frequency converter, the PID controller and the image acquisition module and is used for prejudging the driving speed of the bridge inspection vehicle according to the image information acquired by the image acquisition module on the one hand and used for correcting the driving speed prejudging process according to real-time control information sent by the PID controller. According to the bridge inspection vehicle frequency conversion control system, the defects in the prior art can be overcome, and the real-time computation amount of the PID controller is decreased by presetting the driving speed.