The invention provides a preparation method of cobalt boracylate, belonging to the field of the preparation of composite material accelerating agent. The preparation method comprises the following steps: mixing neodecanoic acid, isooctyl acid, glacial acetic acid, dimethylbenzene and cobalt hydroxide, carrying out acid-base neutralization reaction, and obtaining an intermediate product after the neutralization reaction is finished; adding tributyl borate into the obtained intermediate product and carrying out boracylate reaction, adding calcium borate as additive simultaneously, and obtaininga reaction product, namely, cobalt boracylate after the boracylate reaction is finished. In the preparation method, the neodecanoic acid, the isooctyl acid, the lower fatty acid glacial acetic acid and the dimethylbenzene are matched and carry out the acid-base neutralization reaction together with the cobalt hydroxide to generate the intermediate product; the reaction velocity can be improved andthe forming of the intermediate product is accelerated due to the effects of the glacial acetic acid and the dimethylbenzene; in addition, in the final boracylate reaction, as the calcium borate as the additive is added together with the tributyl borate, the reaction time is effectively shortened, and the insoluble substance performance and the anti-static property of the cobalt boracylate whichis prepared finally are improved.