Crystalline carbon nitride (C-C3N4) doped with cerium oxide (CeO2) was synthesized using ionothermal method to increase the photocatalytic activity for H2 production. Graphitic carbon nitride (g-C3N4) obtained from direct pyrolysis of urea at 550°C was subsequently annealed with a mixture of KCl and LiCl to obtain C-C3N4. CeO2 was doped onto C-C3N4 and g-C3N4 via calcination at 550°C. XRD analysis showed the formation of high intensity C3N4 and CeO2 peaks in C-C3N4/CeO2, meanwhile g-C3N4/CeO2 only showed CeO2 peaks. FTIR analysis confirmed all the samples contained C3N4 polymeric structure. The specific surface area of g-C3N4 was measured at 61 m2/g. The surface area increased to 92 m2/g when g-C3N4 transformed into C-C3N4, and further increased to 106 m2/g on C-C3N4/CeO2. The photocatalytic activity for H2 gas production showed significant increase of H2 rate on C-C3N4/CeO2 compared to g-C3N4/CeO2 and g-C3N4. The high crystallinity and high surface area were suggested to enhance photocatalytic activity of C-C3N4/CeO2 in visible light presumably due to the increase of electron and hole lifetimes.