A COF package structure includes a flexible substrate and a chip. A chip mounting area is defined on an upper surface of a flexible base of the flexible substrate. A circuit layer of the flexible substrate includes a plurality of first upper leads, second upper leads, first conductive vias and lower leads. The second upper leads are disposed in the chip mounting area and divided into groups, and each second upper lead has a second inner end and an upper pad opposite to each other. The upper pads of each group are arranged layer by layer into at least two rows. There are two upper pads symmetrically arranged on both sides of a reference line of each group on at least one row furthest from the second inner ends. The first conductive vias connect the upper pads and the lower leads. The chip is mounted in the chip mounting area.