A preparation method of a wound trapezoidal battery core and the trapezoidal battery core, in the trapezoidal battery core, intervals are formed between the inflection points of the 1-Nth circles of adjacent coils, and the inflection points of the N-M circles of adjacent coils are There is no space between them, and the cross-sectional shape of the cell after hot pressing is trapezoidal. When the battery core of the present invention is wound, from the first turn to the Nth turn, a piece of winding needle is inserted for each turn, so that the winding diameter of each turn is increased by an expansion width relative to the winding diameter of the previous turn, so that There is an interval between the inflection point of the nth coil and the n+1 coil; from the Nth coil to the Mth coil, the remaining coil is wound with a fixed winding diameter; the trapezoidal groove is used The jig heat-presses and shapes the winding core, and after hot-pressing and shaping, a battery core with a trapezoidal cross-sectional shape is obtained. The trapezoidal battery cell obtained by the present invention can maximize the reserved space for the use of equipment, increase the design capacity of the battery cell, and can evenly distribute the stress on the transition slope of the battery cell, and can avoid the problem of deformation of the battery cell after long-term cycling.