In this study, BaCe_0.5Zr_0.3Y_0.2O_3-δ (BCZY) electrolyte was studied as a high proton conducting electrolyte for proton-solid oxide electrolyzer cell (P-SOEC) applications. For using high proton conducting electrolyte, there are some advantages such as (1) Reduce Cr evaporation and mitigate materials degradation, (2)Use of lower cost metals, alloys and coatings, (3) Ease of gas sealing, (4) Reduced cost of hydrogen production. For the P-SOEC, a very dense proton-conducting electrolyte with >95% relative density is needed. In this study, a modified solid-state reaction method was developed. With multi-step processes, BaCe_0.5Zr_0.3Y_0.2O_3-δ powder was obtained at a temperature as low as 1200°C which is 200°C lower than that used in the traditional solid-state reaction method (1400°C). For undoped BCZY, 90% relative density was obtained when sintered at 1250°C. With the addition of sintering aid, BCZY may reach 97% relative density at the same temperature. It is believed that the presence of sintering aid promotes the densification of BCZY due to liquid-phase sintering mechanism. In addition, the conductivity of highly densified BCZY reached 5.86×10^-3 S/cm at 700°C. The crystal structure and microstructure of sintered BCZY was also characterized using XRD and field-emission SEM.