Abstract: Using the titanium tetrachloride as raw material, nano-TiO₂ compound membrane was synthesized by the hydrolysis precipitation method. The crystal structure, morphology of TiO₂/diatomite-based porous ceramics were characterized by XRD, TEM, FTIR and so on. Composite as the air filter core body, the photocatalytic kinetics of materials was investigated by the degradation for formaldehyde. The results indicate that nano-TiO₂ calcined at 600℃ is anatase, and the average grain size of TiO₂ is 10.6 nm. Nano-TiO₂ thin film is loaded strongly on the carrier surface, and the thickness is 300-450 nm. The Si-O-Ti bonds between the interface of the coating layer and the surface of nano-TiO₂ particle are formed. The elimination ratio of the composites for formaldehyde with the concentration 1.302 mg/m³ reaches 94.6% in 240 min under an ultraviolet lamp irradiation. Kinetics study showed that the kinetics of formaldehyde degradation inaction can be described by Langmuir-Hinshelwood model. The rate constant of the gas phase photocatalytic first order reaction and adsorption coefficient are 0.576 mg/(m³·min) and 0.048 m³/mg respectively. The kinetic equations of photocatalysis are established.