The invention discloses an all-solid-state battery with low interface resistance and a preparation method of the all-solid-state battery, the all-solid-state battery comprises an integrated battery cell, and the integrated battery cell comprises a positive electrode current collector layer, a positive electrode layer, a buffer layer, an organic-inorganic composite electrolyte membrane, a negativeelectrode layer and a negative electrode current collector layer which are arranged in sequence; the organic-inorganic composite electrolyte membrane comprises a high-molecular polymer matrix, a lithium salt and an inorganic filler, the high-molecular polymer matrix is selected from polyvinylidene fluoride or a polyvinylidene fluoride-hexafluoropropylene copolymer; the lithium salt is selected from at least one of LiTFSI, LiFSI, LiClO4, LiPF6, LiBF4, LiBOB, LiDFOB and LiPF2O2. According to the invention, a layer of soft contact is formed between hard interfaces of the positive electrode and the negative electrode, multiple layers of films are integrally formed, different component film structures are seamlessly interconnected, and the interface problem of the solid-state battery is effectively improved. The solid-state battery provided by the invention has excellent capacity exertion and cycling stability, and the preparation method is high in efficiency and low in cost.