The invention discloses europium-activated tellurate red phosphor and a preparation method of the europium-activated tellurate red phosphor and belongs to the technical field of rare earth luminescent materials. The chemical general formula of the red phosphor is Ala1-xEuxMgTeO6, wherein A refers to the element Na or K, the doping concentration range of the active ion Eu is 0 to 1, and x is less than or equal to 1. The preparation method of the red phosphor comprises the steps that (1) according to the molar ratio in the chemical general formula, corresponding raw materials are weighed accurately and ground and mixed uniformly; (2) the raw materials which are ground and mixed uniformly in the step (1) are roasted at a high temperature in the air; (3) a roasted product obtained in the step (2) is post-processed, and then the red phosphor is obtained. The red phosphor can emit strong red light after being motivated by near ultraviolet light or blue light, and the peak wavelength is about 619 nm; besides, since the red light is high in color purity, the red phosphor can be used for manufacturing of a white LED, the color rendering index of the white LED can be improved, and the color temperature of the white LED can be lowered.