The invention provides an electrochemical levelling and polishing processing method with nanometer precision and a device thereof, relating to an electrochemical etching levelling and polishing technology. The device is provided with a cutter with nanometer levelling precision, an electrochemical reaction control system capable of accurately controlling the thickness of an etching levelling agent liquid layer in nanoscale, a solution circulating device, a solution thermostat and an automatic control system. The method is implemented by the following steps: preparing the cutter with nanometer levelling precision to serve as an electrochemical working electrode, and placing the cutter at the bottom of a container together with a workpiece; immersing the cutter in a solution, starting an electrochemical system, generating the etching levelling agent on the surface of the cutter, compressing the etching levelling agent liquid layer on the cutter surface into a nanoscale thickness, and regulating and controlling the thickness of the etching levelling agent liquid layer; driving a tri-dimensional micro-drive device, leading the cutter to approach the workpiece gradually, and regulating and controlling the distance and parallelism between the workpiece surface and the cutter; and leading the cutter to move toward the workpiece surface, and enabling the constraint etching levelling agent liquid layer on the cuter surface to contact with the workpiece surface until the whole workpiece is etched, leveled and polished.