In this work, CQDs/MIL-101(Fe)/g-C3N4 photocatalyst was facilely fabricated, which exhibited prominent photocatalytic properties for the degradation of methylene blue (MB) aqueous solution. The photocatalytic degradation rate of MB by CQDs/MIL-101(Fe)/g-C3N4 composite material was found to be 124.7 times higher than that of MIL-101(Fe) and 1.3 times higher than that of MIL-101(Fe)/g-C3N4. Based on the different positions of CQDs in the structure, it is proposed that both Type-II and Z-scheme heterostructure models may exist simultaneously in the CQDs/MIL-101(Fe)/g-C3N4 composite material. The enhancement mechanism of CQDs in promoting the migration and separation of visible light-generated carriers in the ternary composite material is under discussion.