(YxGd1-x)BO3:Eu phosphor particles were prepared by the spray pyrolysis. The effect of preparation conditions such as Y/Gd ratio, preparation temperature, boric acid concentration used as boron source, post-treatment temperature, and doping concentration of Eu, on the crystallinity, morphology, and luminescence characteristics of particles were investigated. To control the morphology of particles, colloidal solution obtained by aqueous solution method was introduced in the spray pyrolysis. The borate particles prepared by the spray pyrolysis from the aqueous solution had low thermal stability because of low melting point of boron component and hollowness of as-prepared particles. The as-prepared particles prepared from the colloidal solutions had higher thermal stability than that of particles prepared from the aqueous solution. The maximum photoluminescence intensity of particles prepared from the colloidal solution was 145% of that of particles prepared from the aqueous solution.