The dynamic behaviour of a fuel cell under varying of load is important for control and optimization. Experimental study on dynamic voltage of a HT-PEMFC (high-temperature PEM fuel cell) was conducted under 5 different currents operating on an anodic flow-through mode, dead-end mode with fixed purging intervals and dead-end mode with varying purging intervals after obtaining their forward and backward polarization curves. The results revealed that the hydration/dehydration processes of phosphoric acid used in HT-PEMFC would affect the dynamic behaviour of the fuel cell, and can be concluded by a few observations: (1) Hysteresis phenomenon was captured in the polarization study when cell current is swept from low to high (forward sweeping), then high to low (backward sweeping); (2) Under anodic flow-through mode, the magnitudes of voltage undershoots and overshoots were less severe at high current than those at the low current operation; (3) The peak performance of HT-PEMFC under anodic dead-end mode operation outperformed that under anodic flow-through mode. However, the performance of HT-PEMFC reduced gradually after the purging and the shape of the dynamic voltage curve under the longest purging interval overlapped with that under shorter purging intervals.