The present invention relates to a method for making nano device. The method includes the following steps: preparing overlay detection mark mask plate of electron-beam and optical exposure machine; applying PMMA resist on substrate, prebaking, electron-beam exposure, developing MIBK:IPA=1:3, time is 1 min, fixing for 30 sec. in IPA solution, evaporation or sputtering metal, stripping in acetone solution, applying secondary electron-beam resist, thickness is 200-250 nm, prebaking, utilizing the method for detecting back scattered electron of mark edge by using electron-beam to detect whole mark on the substrate and small mark of every die, correcting according to measured value, secondary electron-beam exposure, accelerating voltage 50KV, dose 500 u C / sq.cm, beam current 100 Pa, developing MIBK:IPA=1:3, time is 1 min, fixing for 30 sec in IPA solution, optically exposing other pattern for making device, finally forming nano-grade device.