S-TiO2 typically exhibits high photocatalytic activity, but its powdered form makes it difficult to apply practically in environmental treatment. Diatomite from different locations varies in purity and integrity of the diatomaceous earth, making it a suitable catalyst support for synthesizing mixed-phase S-TiO2 catalysts using the sol-gel technique. The synthesized photocatalyst exhibits similar photocatalytic activity to S-TiO2. The NO gas treatment efficiency under the same conditions with different catalyst supports only decreases by approximately 3% within 30 minutes at a reaction rate of 0.0950 min-1, with an optimal mass ratio of 70:30 for S-TiO2 and diatomite. This composite material holds promise for addressing the application of photocatalytic materials in practical environmental treatment, including NO removal and the treatment of other environmental pollutants, as diatomite is a naturally available and environmentally friendly material.