The invention provides a trapezoidal ion battery and a preparation method thereof. The trapezoidal ion battery comprises a positive electrode plate, a negative electrode plate, diaphragms and electrolyte. The positive electrode plate, the negative electrode plate and the diaphragms are all trapezoidal, and corresponding side length relation of the positive electrode plate, the negative electrode plate and the diaphragms includes that the side length of the positive electrode plate is smaller than that of the negative electrode plate while the side length of the negative electrode plate is smaller than that of the diaphragms. One diaphragm, the negative electrode plate, the positive electrode plate and the other diaphragm are sequentially laminated to form a cell, the upper surface and thelower surface of the cell are coated with the diaphragms, and the electrolyte are positioned on the positive electrode plate and the negative electrode plate in the cell. The trapezoidal ion battery and the preparation method thereof have advantages that trapezoidal spaces of intelligent wearable devices, unmanned aerial vehicles, inspection robots and the like are used to the greatest extent, equipment battery energy density is improved, and accordingly endurance of equipment is effectively improved.