The invention relates to a method for preparing a small-granularity cerium terbium lanthanum phosphate rare earth product with high luminous efficiency. The method comprises the following steps of preparing a 0.2-0.5 mol/l rare earth chloride or nitrate solution and a 0.5-1.0 mol/l precipitant containing phosphate radical; adding the raw materials into a reactor containing a base solution of which the temperature is 30-50 DEG C and the acidity is 0.1-0.5N and reacting; after the precipitation is carried out, aging, washing with water, carrying out vacuum dehydration and microwave drying, sieving and firing to obtain the cerium terbium lanthanum phosphate product. According to the invention, the raw materials are subjected to precipitation, feeding and mixing by virtue of a precision control system, the control process is divided into four stages, the precipitation process is effectively controlled in the four stages, the morphology and performance of a precipitate particle are improved, the product obtained by vacuum filtration, microwave drying and other methods has excellent quality in the aspects of impurities, granularity, the crystal morphology and the like, the method meets the industrial needs and is suitable for being popularized and the preparation is simple.