The invention discloses a low-temperature sintering temperature-stable microwave dielectric ceramic and a preparation method thereof. The composition formula of the low-temperature sintering temperature-stable microwave dielectric ceramic is Bi14W2O27. The preparation method comprises the steps of (1) weighing and batching original powder of Bi2O3 and WO3 with the purity being over 99.9% according to the chemical formula Bi14W2O27; (2) carrying out wet ball-milling and mixing on raw materials obtained in the step (1) for 12 hours, taking distilled water as a solvent, drying, and then, pre-sintering in an air atmosphere for 6 hours at the temperature of 700 DEG C; (3) adding a binder into powder prepared in the step (2), granulating, then, carrying out compression molding, and finally, sintering in the air atmosphere for 4 hours at the temperature of 800-820 DEG C, wherein a polyvinyl alcohol solution with the mass concentration of 5% is adopted as the binder, and the dosage of the binder accounts for 3% of the total mass of the powder. According to the ceramic prepared by the preparation method, the sintering at the temperature of 800-820 DEG C is good, the dielectric constant reaches 12-13, the quality factor (Qf) reaches up to 61,000-84,000GHz, the temperature coefficient of resonance frequency is small, and the ceramic can be subjected to low-temperature co-sintering together with a Ag electrode, so that the ceramic has a great application value in industries.