The invention discloses a method for preparing p-hydroxybenzaldehyde via photocatalysis. The method comprises the following steps: adding a certain amount of p-hydroxybenzyl alcohol, a reaction solvent and a mesoporous TMDs catalyst into a quartz reaction container, and performing a visible light catalytic reaction to obtain a target product p-hydroxybenzaldehyde. A photocatalytic process adopted in the method is simple and convenient in operation, and simple in posttreatment; in addition, the mesoporous catalyst has a relatively large surface area, relatively large pore capacity, an adjustable pore diameter and high catalytic activity.