Abstract: A scan-retrace optical scanner model without rotating direction change of the driving motor, was proposed. The scanner's fly-back angular velocity doubled its scan trip. By utilizing partially-cut gear transmission and spring-damper element, the system could realize stable scanner rotating direction change without the shift of driving motor current direction. Because the energy was mainly provided by the resilient member in the scanner rotating direction changing phase, it meant the driving motor was less demanding in the system than that in the traditional one. The scanner was subject to motor's driving torque and resilient member spring-back torque in scan and retrace trip. This design helped to eliminate gear clearance efficiently and could assure transmission accuracy of the system. Compared with traditional motor directly driving scanning system, rotational driving motor doesn't need current direction shift in this system, thus control system design is simplified, performance of driving motor is decreased and scan rate is improvd. This model plays a good potential solution for the compact, large trip, high precision optical scanning system development.