The invention discloses a method for preparing a 
solid electrolyte by using 
lithium lanthanum zirconium oxide precursor coated 
powder. The method specifically comprises the steps of dissolving a certain amount of 
lanthanum nitrate and 
zirconium nitrate into water, adding a precipitator, namely 
ammonium carbonate, controlling the pH value to ensure that La<3+> and Zr<4+> ions are simultaneously precipitated, and filtering and washing the precipitate; weighing a certain amount of 
lithium oxalate, dissolving 
lithium oxalate into water, adding the precipitate into the lithium 
oxalate solution, stirring, evaporating, crystallizing, and separating out lithium oxalate 
crystal on the surface of the precipitate to form precursor 
powder with a coated structure. The prepared 
powder has the advantages of uniform mixing, fine grains, high purity and the like; through the formed specific coated structure, the 
calcination temperature of the powder is low, the 
sintering time of the powder is short, and the room-temperature lithium 
ion electric 
conductivity of the sintered lithium 
lanthanum zirconium oxide is more than 2.2*10<-4>S / cm. According to the method, the process is simple, the cost is low, the preparation conditions are easy to control, and the prepared 
solid electrolyte is good in electrochemical stability and high in electric 
conductivity and can be used for preparing all-
solid-state lithium 
ion batteries.