Magnetic polyvinyl alcohol-based g-C3N4 composite (MPg-C3N4) was synthesized as a heterogeneous catalyst. It was characterized by various analyses such as FT-IR, XRD, FE-SEM, TGA, EDX, and VSM. For showing the catalytic merits of MPg-C3N4, it was used in the synthesis of acridinedione and 4H-chromene derivatives in a highly efficient yield. Various aldehyde derivatives were used to show the merits of the MPg-C3N4. High yield, short reaction time, easy separation, mild condition reaction, simple purification, non-toxic solvents, and reusability are the advantages of using polymer-based heterogeneous MPg-C3N4 catalyst to synthesize acridinedione and 4H-chromene derivatives. Also, the intended products were purified by simple crystallization.