The invention discloses a method for reclaiming and preparing lithium cobalt oxide from waste lithium ion batteries. The method is characterized in that the waste lithium batteries are disassembled and the shells are removed to select positive plates with the anode made of lithium cobalt oxide; the positive plates are crushed and screened to obtain minus sieve containing waste lithium cobalt oxide as the main component; in a constant-temperature resistance furnace, caking agent and conductive agent acetylene black in the minus sieve are removed in high temperature, sodium hydroxide is adopted to remove aluminum, and filtering, washing and drying are performed to obtain inactive lithium cobalt oxide containing little impurity; the content of lithium and cobalt is detected in the inactive lithium, then lithium carbonate with proper proportion is mixed in, at last, active lithium cobalt oxide battery material is synthesized by high-temperature agglomeration in a muffle furnace. Through the application of the method, the coefficient of recovery of cobalt in waste lithium ion batteries can reach more than 95.0 percent, and the coefficient of recovery of lithium can reach more than 97.0 percent.