Recently, lithium ion batteries with high working voltage, high energy density and good cycle ability have been widely adopted as the most promising portable energy source in electronic devices. However, lithium secondary batteries have some safety problem due to using the liquid electrolytes. Solid electrolytes are one of the very important keys to realize all-solid-state secondary batteries with high safety and high energy density. The garnet structure solid electrolyte is great candidate solid electrolyte in all solid lithium ion battery. It is better than others in terms of electrochemical stability and high ionic conductivity. In this studies, garnet LLZO was doped with a different elements via. coprecipitation method in order to increase the ionic conductivity and structure stability. Bare LLZO powder with tetragonal structure was changed into cubic structure when the chemical elements were doped. Especially, the best doped LLZO showed an excellent crystallization with a high intensity peak, indicating the highest ionic conductivity of 7.11 x 10^-4 S/cm due to the excellent sinterability.