Display omitted •Novel S-CQDs/hollow tubular g-C3N4 photocatalyst was successfully fabricated.•HTCN-C(2) exhibited excellent photocatalytic activity for Escherichia coli photodestruction.•The changes of Escherichia coli morphology and inside contents were verified by SEM images.•h+, O2− and OH radicals participate in the photocatalytic degradation process.•Cycle experiments revealed the outstanding photo-stability and reusability. Microbial contamination and antibiotic pollutions diffusely exist in wastewater system, and contaminated water poses a threat to public health. Therefore, there is a need to effectively remove biohazard and antibiotic contamination from wastewater systems. In this paper, sulfur doped carbon quantum dots (S-CQDs)/hollow tubular g-C3N4 photocatalyst (HTCN-C), prepared via ultrasonic assisted synthesis strategy, was regarded as an efficient catalyst for the degradation of antibiotic (tetracycline) and destruction of a typical Gram-negative bacterium (Escherichia coli) in imitated wastewater system. The unique structures of hollow tubular g-C3N4 and loading of modified carbon quantum dots enhanced electron transfer and charge separation, leading to a significant improvement in photocatalytic efficiency. Benefiting from these merits, the optimized catalysts (HTCN-C(2)) exhibited superior performance with a reaction rate of 0.0293 min−1 for tetracycline (TC) degradation and 99.99% destruction of Escherichia coli under visible-light irradiation. Moreover, the characterization of UV–Vis diffuse reflectance spectra, photoluminescence technique, transient photocurrent responses and electrochemical impedance spectroscopy also verified the good optical and electrochemical properties of resultant samples. Our current work indicates that HTCN-C has great potential in degradation of antibiotic and destruction of bacterium for practical wastewater treatment.