Photocatalysis is widely employed to treat emerging pollutants in water, due to its well-organized attributes. Self-sensitive carbon nitride (SSCN) represents a novel class of non-metallic photocatalyst that has garnered significant attention for its distinctive properties in contrast with traditional graphitic carbon nitride (g-C₃N₄). However, their visible-light photodegradation effect remained still to be enhanced. Here, SiO₂ microspheres were initially synthesized by the St?ber method, followed by the preparation of SiO₂/SSCN composites through an in-situ hydrothermal process. Their microstructure, phase structure, and photoelectric properties were systematically investigated using a combination of characterization techniques. It is discovered that the SiO₂ within the composites effectively disperses in the SSCN. The obtained composite material was then applied to photocatalytic degradation of antibiotic pollutants in water, exhibiting enhanced degradation activity, which was closely correlated with the quantity of SiO₂. At mass ratio of SiO₂ to SSCN of 0.04 : 1, the composite achieved optimal photocatalytic activity and demonstrated good stability. After irradiation for 60 min, 42% of tetracycline hydrochloride was degraded, and the photocatalytic degradation efficiency remained at 38% after 5 cycles. Furthermore, incorporation of the SiO₂ component offers supplementary sites for the dispersion of SSCN, mitigating serious agglomeration phenomenon of SSCN. This facilitates the rapid decomposition of 1,3,5-triazine oligomers (TBO) on the surface of SSCN under light irradiation, and the optimizing content of TBO on surface active sites. Consequently, utilization efficiency of visible light on SSCN is significantly improved, and a higher separation rate of photogenerated electron-hole pairs is simultaneously observed. These attributes culminate in significantly improved photocatalytic activity for the degradation of tetracycline hydrochloride on SSCN under visible light irradiation. Above advantages may position the as-synthesized SiO₂ dispersed SSCN as prospective candidate for practical application. Therefore, this research offers a novel route for enhancing the photocatalytic activity and stability of catalysts.