The invention discloses a deflection angle measuring and correcting system and method of a laser range finder. The system comprises carrier device, a data processing unit, a control unit, a laser range finding unit, a calibration plate and a position fixing standard member. The external assembly of the system only comprises one calibration plate, and the carrier device, the laser range finding unit, the data processing unit and the control unit are inherent devices of the system itself, so that the manufacturing and the operation of the system are very simple; after a pitch angle is determined to be 0, whether the deflection angle of the laser range finder meets the requirement can be determined by the system, so that the calculation of the deflection angle is simplified, and the system is simple, convenient and easy to handle; in addition, the accuracy of multi-measurement results is high, and the system has the advantages that the cost is low, the operation is simple, and the precision meets a practical requirement.