A new method was developed to grow up the single-crystal miero-plater of organic nonlinear optical crystal 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). DAST micro-crystal was prepared by the method of substrate-supported rapid evaporation crystallization, then placed in a circumstance of saturated vapour pressure of methanol to undergo a self-assembly way and form single-crystal micro-plate. The obtained DAST micro-plate not only has uniform thickness but also exhibits excellent crystal surface quality. Furthemore, the ultraviolet-visible absorption spectra, fluorescence emission spectra and second-order nonlinearity of the micro-plate were also studied carefully.