The invention discloses a boron-containing plastic crystal polymer and a preparation method and application thereof. The preparation method includes the following step of curing a mixture containing plastic crystals, metal salt, monomers and a photoinitiator to obtain the boron-containing plastic crystal polymer. The plastic crystal polymer prepared by the method can be used as an all-solid electrolyte, no liquid additive is added, and the obtained electrolyte room temperature ion conductivity can be as high as 3.6*10<-4> S/cm; and meanwhile, the high sodium ion migration number and the wide electrochemical window are be exhibited and can be as high as 4.7 V. In addition, in order to construct a stable electrode/electrolyte interface to reduce the interface impedance, a composite positiveelectrode and negative electrode are prepared for positive and negative electrode modification of a sodium ion battery, and the finally-assembled all-solid sodium ion battery exhibits the good rate capability and the cycle stability at room temperature, the specific discharge capacity at room temperature can be as high as 104.8 mAh/g, and the capacity retention rate is 85.4% after circulation by 80 circles.