A new hot-forging method by means of direct resistance heating is investigated aiming at the long produce time and large energy consumption of traditional hot forging. The hot upsetting experiments with cylindrical billet of 42CrMo4 are performed. The influences of initial contact force, surface quality of the billet and current intensity on the heating temperature are researched. The results of the experiments show that the billet can be heated quickly to forming temperature by the approach. The relatively low initial contact force is useful to increase the heating temperature. The heating temperature is proportional to the square of the current intensity, and the heating temperature is seriously affected by the surface quality. During the forming process the billet cooling rate is effectively decreased and the forming time is extended in relation to the resistance heating.