The invention discloses a method for preparing cobalt octoate by using LiCoO, an anode material of a waste lithium battery, comprising the following steps: carrying out acidolysis on powder of the LiCoO, the anode material of the waste lithium battery by chemical extraction and back extraction, removing Fe and Al by chemical precipitation, filter pressing and deslagging, adding P204 self-made auxiliary extractant to remove impurities and adding P507 self-made auxiliary extractant to extract and separate Co from Li to prepare CoSO4 liquid with content of 75-80%, precipitating raffinate to prepare LiCO3 with primary deposition rate more than 75%, carrying out double decomposition reaction on sodium octoate obtained after saponification reaction between the prepared CoSO4 liquid and octoic acid as well as sodium hydroxide and preparing the product of cobalt octoate liquid through washing, standing to be layered, dehydrating, regulating metal contents and filtering. The rate of recovery of cobalt from the powder of the LiCoO, the anode material of the waste lithium battery is more than 97%.