Among many kinds of electrolytes, Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) ceramic electrolyte has a few focal points such as relatively low price, excellent resistance to air and moisture, high ionic conductivity, and environmental safety. Besides, LATP has a disadvantage in that it exposes batteries to degradation due to the interfacial layer formed after it touches metallic lithium because of the titanium reduction reaction. Herein, we report our results on the strategy of anion doping in LATP structures by Si (LATSP). The LATSP samples with various Si content were synthesized by a simple molten flux method at 800 °C with a pure phase. The structure, morphology, and ion-transport properties were analyzed. It was demonstrated that increasing Si doping content has significant positive effects on electrolyte conductivity.