The large and high quality DAST crystal can be obtained by using the seed crystal method, while the DAST seed crystal surface quality directly affect the quality crystal. Using selfmade DAST source powder, DAST seed crystal was grown by the solution cooling method, and the crystal surface was investigated. DAST source powder was tested by the infrared spectrum, and it was found that DAST crystal had the water absorptivity. The surface morphology of DAST seed crystal was detected by the differential interference fiber lens and atomic force microscope, the surface defects such as pits and growth steps existed in the DAST seed surface.