The invention discloses a method for degrading organic pollutants in wastewater by catalyzing percarbonate. The method comprises the following steps: adding a g-C3N4 catalyst which is subjected to protonation treatment into wastewater, and stirring and adsorbing to form a mixture under a dim environment; adding percarbonate into the mixture to form a reaction system; putting the reaction system within an illumination range of visible light, catalyzing and activating percarbonate by g-C3N4 to degrade organic pollutants in wastewater, wherein protonation comprises the following steps: adding concentrated sulfuric acid into blocky g-C3N4 to mix, stir and perform ultrasonic treatment, thereby obtaining a mixture; mixing the mixture with water by stirring, thereby obtaining milk white suspension liquid, centrifuging, washing and drying the milk white suspension liquid to obtain acidified g-C3N4; thermally reflowing acidified g-C3N4 for 4-8 hours at a temperature of 50-75 DEG C, performing suction filtration, washing and drying to obtain g-C3N4 subjected to protonation. According to the method disclosed by the invention, the effect of degrading the organic pollutants in wastewater is remarkable, a degradation rate is high and degradation is stable.