The invention discloses a preparation method of a liquid lithium ion pole piece battery pack. The preparation method comprises the following steps: 1, preparing a pole piece capacity unit; 2, preparing a to-be-injected activated lithium ion pole piece battery pack; 3, injecting a lithium ion electrolyte; 4, performing activation; and 5, after activation, forming a filling type sealed packaging shell for completely sealing and packaging the periphery of the exterior of the battery pack and filling all residual spaces in the battery pack through filling type sealed packaging, so as to realize the isolation of the battery pack from the external environment and the fixation of components of the battery pack, thereby obtaining the liquid lithium ion pole piece battery pack. Compared with the complex traditional process route, the traditional battery pack manufacturing process is simplified into stacking, welding, liquid injection, activation and packaging, so that the process route is shortened, the productivity is improved, the preparation of the battery pack is easier to control, meanwhile, the series formation of the whole battery pack in the same environment is realized, the consistency between single battery cells is improved, and the performance of the battery pack is improved.