The invention relates to a square flexibly-packaged battery and a manufacturing method therefor. The manufacturing method comprises the steps of stacking and winding a negative plate, a first diaphragm, a positive plate and a second diaphragm on the outer side of a circular winding needle in sequence, and forming a circular winding core outside the circular winding needle; transforming the circular winding needle into a polygonal winding needle to drive the circular winding core to be transformed into a polygonal winding core; and applying pressure on the polygonal winding core to form a square winding core. The negative plate, the first diaphragm, the positive plate and the second diaphragm are wound into the circular winding core through the circular winding needle; the supporting force of the circular winding needle on the circular winding core is distributed around the circumferential surface, so that the stress in the interior of the circular winding core is more uniform; then the circular winding core is pressed into the square winding core; and the stress on the interior of the formed square winding core is still uniform in each direction, so that the expansion degree in each direction caused in the charging-discharging process of the battery tends to be consistent, distortion of the battery is further prevented, and the reliability and the safety of the battery are effectively improved.