The invention discloses a preparation method of an energy-efficient and environmentally-friendly disperse dye. The method comprises the following steps: carrying out a coupling reaction on a diazo salt and a coupling component to obtain a corresponding azo compound, adding an alkali to to adjust the pH value of the obtained system to 2-7.5, carrying out heating crystal transformation to obtain a stable crystal form, press-filtering obtained crystals, and washing the press-filtered crystals with water to obtain a dye filter cake. The method mainly has the following advantages: 1, the pH value of the system is improved, so obtaining of the stable crystal form through dye crystal transformation is facilitated, and electricity and time are saved in the sand milling process; 2, parts of the disperse dye dissolved in a mother liquor can be recovered, so the content of organic matters in the mother liquor is greatly reduced, and the wastewater treatment difficulty is reduced; 3, the filter cake mother liquor is rich in ammonium sulfate (or sodium sulfate), and can be used to prepare ammonium sulfate (or sodium sulfate), so wastewater recycling is realized; and 4, the amount of water for washing is greatly reduced, so the wastewater discharge is greatly reduced.