Abstract: During the operation of HXD1 electric locomotives in complex mountainous areas, "wheel polygonization" is prone to occur due to various factors such as wheel-rail contact stress, wear, material fatigue, and wheel-rail incompatibility. To investigate the influence of different states of wheel polygon wear on locomotive dynamics, a rigid-flexible coupling dynamics model of the HXD1 locomotive-track system is established. This model calculates the effects of the order and amplitude of wheel polygonization on locomotive dynamic performance indicators, including derailment coefficient, wheel load reduction rate, and vibration acceleration. Based on these findings, the threshold for polygon turning is explored. The results indicate that wheel polygonization deteriorates locomotive dynamic performance with increasing speed, order, and amplitude. As the order of the wheel polygon increases, the safety threshold for the polygon amplitude decreases. Specifically, the amplitude limit for a 30th-order polygon is 0.06 mm, while the corresponding limits for 28th, 26th, 24th, and 22nd-order polygons are 0.08 mm, 0.18 mm, 0.23 mm, and 0.27 mm, respectively.