The invention discloses a diatomite decoration brick and a molding method thereof. The diatomite decoration brick is produced from, by weight, 30-60 parts of diatomite, 15-50 parts of calcined kaolin, 5-12 parts of a composite inorganic adhesive, 2-6 parts of ceramic fibers and 2-6 parts of an inorganic pigment. The molding method of the brick comprises the following steps: uniformly mixing diatomite, calcined kaolin, the composite inorganic adhesive, the ceramic fibers and the inorganic pigment; spraying water onto the above uniformly-premixed raw materials to wet the raw materials, placing the wetted raw materials in a die, carrying out compression molding, drying the molded mixture in a shady and cool place, and removing the die to obtain a rough blank; and placing the molded rough blank in a tunnel furnace, calcining the rough blank at 150-400DEG C for 2-10h, and cooling the calcined rough blank to obtain the diatomite decoration brick. The diatomite decoration brick has high strength and high air purifying ability, is especially suitable for decorating interior and exterior walls of civil buildings, and can be widely applied to factories, subways, food and drink places, entertainment places, conference centers and theaters.