The invention provides a method for synthesizing nano material, in particularly a synthesizing method aiming at needle shape ZnSe semiconductor nano crystal. The method includes steps as follows: heating stirring simple substance Se or supersonic dissolving into TOP for obtaining Se precursor; stirring and mixing zinc source and non-coordination solvent octadecylene and long chain alkylamine for obtaining Zn precursor protected by inert gases; processing 'homogenization' to Zn precursor, then raising temperature to a synthesizing reaction temperature (300-350 DEG. C) protected by inert gases;adding Se precursor into Zn precursor rapidly and reacting some time for obtaining original solution crude product of needle shape ZnSe nano crystal, adding a mixed solvent composed of high polarity organic solvent and low polarity organic solvent for washing and centrifugating, finally obtaining a transparent solution of needle shape ZnSe nano crystal by using low polarity organic solvent dissolving. The method has advantages of simple operation, little environmental pollution and better crystallinity degree.