In view of the thermal management of power batteries, the new liquid-cooling structure of 18650 cylindrical lithium ion battery array and its cooling effect were studied. An immersion cooling method combined with a checkerboard topology shunt structure was proposed. And by combining the shape and array arrangement of the lithium ion battery, a simple and reasonable immersion cooling topology based on the battery array was formed. Under this new cooling structure, the single model and module model of the battery array were established. Through the numerical simulation, the temperature distribution of the single and module models at every moment was analyzed, and the feasibility of replacing the module model with the single one was verified. On the basis of ensuring the calculation accuracy of the single model, numerical simulations on the layout of the inlet and outlet of the cooling channel were carried out. The results show that the same-side arrangement and the different-side one are almost the same in the pressure drop, but the same-side arrangement is superior to the different-side arrangement in terms of cooling effect. Moreover, with the increase of the heat generation of the battery and the extension of the heating time, the advantages of the arrangement of the inlets and outlets on the same side are more obvious.