Abstract: ⁹⁰Sr sources are high-energy β radioisotope sources, which have been applied in many fields. It’s necessary to study the influence of impurity content and powder particle size on the mechanical properties and sintering stability of strontium titanate ceramic source cores because of the effect of strontium titanate ceramic cores’ performance on the safety and production technology difficulty of ⁹⁰Sr sources，which will provide references for the rational formulation of the purification, preparation process and the cold-pressing sintering process of strontium titanate source cores. Orthogonal experiment method was adopted in this study to simplify the experimental steps and achieve better experimental results. The contents of calcium, barium, zirconium and powder particle size were taken as four factors, and the control experiment was designed according to orthogonal table L₉ (3⁴). The performance of the sintered strontium titanate cores were tested under different impurity content and powder size conditions, including density, size, compressive strength and hardness. The results showed that under the condition of fixed cold pressure sintering process parameters, the particle size and impurity element zirconium had obvious influence on the performance of strontium titanate ceramic cores. The best particle size is 10 μm and the content of zirconium must be controlled under 1%. The impurity elements calcium and barium have relatively little influence on the performance of strontium titanate ceramic cores. Their contents must be controlled under 2% and 4%.