The invention discloses a preparation method of a metal-doped manganese dioxide photocatalyst for coking wastewater treatment. The method comprises the following steps: weighing 1.100-1.104 g of potassium permanganate, and adding the potassium permanganate into a 100 mL beaker; and adding 35-37mL of deionized water and 35-37 mL of ethanol into the beaker, and performing sufficient stirring to obtain a purple-red solution. A metal oxide and manganese dioxide are compounded, the metal oxide has a photocatalytic property, and the manganese dioxide has a good photocatalytic property, a large specific surface area and strong adsorption capacity, so the metal oxide composite manganese dioxide has an improved photocatalytic performance, can significantly improve the separation of photogenerated electrons and holes and greatly improve the photocatalytic activity of a catalyst, and can easily convert light energy into energy required by a chemical reaction in order to achieve the catalysis effect, thereby surrounding oxygen and water molecules can be excited to form free negative ions with an oxidizing power, and the ability of the catalyst to treat phenol in the coking wastewater is improved.