The invention discloses a controllable phase change material bag and a preparation method and an application thereof. The preparation method comprises the following steps of (1) performing surface treatment on a metal plate or bar so as to form the metal plate or bar with a rough surface, embedding seed crystal powder which is used for inducing phase change materials into a nucleus into the surface, then putting in a sodium acetate solution, putting the sodium acetate solution in a water bath, and insulating so as to obtain a controllable trigger metal electrode; (2) mixing sodium acetate trihydrate crystal, water and a thickening agent, heating in the water bath and mixing so as to completely dissolve, so that a supersaturated phase transition heat storage solution is obtained, pouring the solution into a stainless steel metal ball, inserting into the controllable trigger metal electrode in the step (1) and a conducting electrode, then packaging, finally, putting in the water bath, and insulating so as to obtain the controllable phase change material bag. According to the controllable phase change material bag, the inherent supercooling defect of inorganic phase change materials is used, so that the controllable heat storage / release of supercooling phase change materials is realized, and the controllable phase change material bag has the advantages of simple preparation process, low equipment cost, short recycling period, stability in heat release and the like.