The invention relates to a mechanical nanoscale high-accuracy linear driving device which comprises a speed-reduction stepping motor, a transmission type conversion assembly and a sensor assembly. Thestepping motor provides power input; the transmission type conversion assembly converts rotation motion into linear motion; and a sensor of the linear differential sensor assembly acquires output displacement information of a linear driver in real time so as to build closed-loop position detection, so that nanoscale high-accuracy linear motion control is realized. A kinematic pair prepressing clearance eliminating measure is arranged in the device, so that the fit clearance and the motion wear are effectively eliminated, and high repeated accuracy is ensured. A flexible link is designed in the device, and a linear output axial preload is provided, so that the output accuracy and the stability are ensured. Compared with a traditional linear driving device, the mechanical nanoscale high-accuracy linear driving device provided by the invention is novel in structure, simple and compact, and has the characteristics of high accuracy, high stability and high space environment suitability.