Technologies regarding camcorder, cellular phone and note book PC etc. have been developing rapidly according to the development of electronics, communication and computer industries. The secondary battery which can be used continuously by recharging has been required for the electric power of such instruments. Therefore, present invention relates to a high-capacity LiMn.sub.2 O.sub.4 compound used for non-aqueous electrolyte lithium ion battery, more particularly, to a method for preparing LiMn.sub.2 O.sub.4 intercalation compound doped with Li and Co ion, which comprises the following steps of : synthesis of spinel type LiMn.sub.2 O.sub.4 powder; dissolving and treating LiMn.sub.2 O.sub.4 powder in the solution to adsorb Li and Co ion; and thermal treatment of said LiMn.sub.2 O.sub.4 to obtain LiMn.sub.2 O.sub.4 doped with Li and Co ion.