The invention discloses low-loss temperature-stable middle-dielectric-constant microwave dielectric ceramic CaTiNbBiO7 and a preparation method thereof. The method comprises the steps that 1, the chemical raw materials of CaCO3, TiO2, Nb2O5 and Bi2O3 powder are weighed and matched according to a stoichiometric formula CaTiNbBiO7; 2, wet ball milling and mixing are conducted on the raw materials obtained in the first step for 12 h, a ball milling medium adopts distilled water, and after drying is conducted, presintering is conducted for 6 h in the air atmosphere of 950 DEG C; 3, a binding agent is added to powder obtained in the second step, granulation is conducted, pressing forming is conducted, and sintering is conducted for 4 h in the air atmosphere of 1,025-1,075 DEG C. The binding agent adopts a polyvinyl alcohol solution with the mass concentration of 5%, and the addition amount of polyvinyl alcohol accounts for 3% of the total mass of the powder. According to the low-loss temperature-stable middle-dielectric-constant microwave dielectric ceramic CaTiVBiO7 and the preparation method thereof, the prepared ceramic is sintered well at 1,100 DEG C or below, the dielectric constant reaches 35.2-36.5, the value of the quality factor Qf reaches up to 48,900-56,100 GHz, the temperature coefficient of the resonant frequency is small, and the microwave dielectric ceramic has great application value in the industry.