the present invention relates to a process for preparing rare earth trichromatic phosphor , comprising the following steps : providing precursors for at least one composition formula selected from the group consisting of cabpo 5 : xeu : ytb , caal r b 1 - r po 5 : xeu : ytb and ca 2 b 5 o 9 cl : xeu : ytb , wherein x = 0 . 02 – 0 . 05 , y = 0 . 001 – 0 . 01 and r = 0 . 5 – 0 . 8 ; grinding and mixing the precursors ; and calcining the product obtained in step at 800 – 1000 ° c . for 3 – 5 hours . according to the present process , only one matrix material and two rare earth reactive ions are required to synthesize rare earth trichromatic phosphor . that is to say , no reducing reagent is needed ; and absence of reducing agent reduces environmental pollution .