Theg-C3N4photocatalystwassynthesized bydirectlyheatingthelow-cost melamine. Themethyl orange dye (MO)was
selected as a photodegrading goal to evaluate the photocatalytic activity of as-prepared g-C3N4. The comparison experiments indicate that the photocatalytic activity of g-C3N4 can be largely improvedbythe Ag loading. The strong acid radical ion (SO42- or NO3-) can promote the degrading rate of MO for g-C3N4 photocatalysis system.