The present disclosure provides a cell and a preparation method thereof. The cell comprises a positive electrode plate (1); a negative electrode plate (2) and a composite solid electrolyte membrane (3) positioned between the positive electrode plate (1) and the negative electrode plate (2). The composite solid electrolyte membrane (3) comprises inorganic solid electrolyte layers (31) and structure supporting layers (32) which are alternately laminated along a laminating direction (D), and has abutted surfaces (S1) respectively abutting against the positive electrode plate (1) and the negative electrode plate (2), an angle between the laminating direction (D) and the abutted surface (S1) is defined as α, and 0°≦α