The invention discloses an electronic-control backlash eliminating gear pair with variable tooth thickness. The gear pair comprises a tooth thickness variable gear I, a tooth thickness variable gear II and an electronic-control backlash eliminating system, wherein the tooth thickness variable gear II is meshed with the tooth thickness variable gear I, the electronic-control backlash eliminating system comprises at least an electronic-control power device used for exerting backlash-regulating axial mechanical force on the tooth thickness variable gear I and the tooth thickness variable gear II, and the direction of the backlash-regulating axial mechanical force is a direction for backlash elimination between the tooth thickness variable gear I and the tooth thickness variable gear II. According to the gear pair, real-time control of axial displacement is achieved through electronic control, then the tooth backlash can be regulated in real time according to backlash regulation requirements, the response is rapid, the transmission accuracy is improved, the volume is small, the structure is simple, the synchronism requirement for control is low, the cost is low, the assembling requirements are easy to satisfy, the tooth backlash and the return difference can be eliminated or reduced timely, the transmission error during reversing can be reduced, therefore the operation and the control are simple and fast, and high adaptability is provided at occasions with high requirements for the integral structure.