Graphitic carbon nitride (g-C3N4) is a non-metallic semiconductor photocatalyst which is widely used in water treatment. Improving the charge separation and transfer efficiency of g-C3N4 has been a hot research topic. In this work, a sulfur-doped algal graphitic carbon nitride (SCN) was synthesized by microwave using thioacetamide as an elemental sulfur dopant. The algal-like structure provided g-C3N4 a higher specific surface area and visible light absorption. Combined with experiments and density functional theory (DFT) calculations, the introduction of S further changed the orbital structure and increased the charge density, leading to a shift of energy level positions as well as enhanced photogenerated electron transport. The combination of morphology adjustment and suitable elemental doping allowed the materials achieve a significant improvement in the photocatalytic degradation performance of organics and the antibacterial activity. The degradation rate of rhodamine B (RhB) by SCN-60mg reached 0.21873 min-1, which was 12 times higher than that of bulk g-C3N4 (BCN). Similarly, SCN-60mg degraded malachite green (MG), neutral red (NR), methyl orange (MO), methylene blue (MB), tetracycline (TC), and ciprofloxacin (CIP) by 100%,93%,90%,97%,79%, and 86%, respectively, within 30 min. Meanwhile, SCN-60mg still exhibited excellent photocatalytic performance in four degradation cycles. In addition, SCN-60mg showed nearly 100% antibacterial efficiency of Staphylococcus aureus (S. aureus) within 1 hour. This study provides a new idea for fabricating effective photocatalysts for complex wastewater treatment.