BiOCl/diatomite composite with enhanced photocatalytic property for the degradation of liquid Tetracycline hydrochloride (TC) and gaseous formaldehyde (HCHO) were successfully prepared by a facile hydrothermal method at different pH value. The structure and morphology characterizations of BiOCl/diatomite composite exhibit that diatomite not only acts as a natural porous support of photocatalyst but also acts as dominant facets regulator at pH = 3 when the doping amount is change, owing to the surface electrical property of the diatomite and interaction between diatomite and BiOCl. This interaction is certified by XPS and FT-IR which indicate that Bi in layer structure of [Bi2O2](2+) group interacts with the O in Si-O-Si bond when the formation of BiOCl with the participation of diatomite. The BET characterization confirms that the increasing amount of diatomite enables the composite with more reaction points for light harvest and molecule adsorption than pure BiOCl. Furthermore, TC and formaldehyde are targeted as degradation objects to test the photocatalytic property of BiOCl/diatomite composite. The optimum photocatalytic property are BiOCl(3-1.2) and BiOCl(12-0.6) at TC degradation and BiOCl (3-0.3) and BiOCl(12-0.6) at formaldehyde elimination, which is much better than that of pure diatomite or BiOCl. The difference of optimum photocatalysts in liquid and gaseous phase systems can be attributed to the photoelectric performances of BiOCl/diatomite composite, which were characterized by DRS, PL, transient photocurrents and the electrochemical impedance spectroscopy technique. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.