-The bi-potential method has been successfully applied for the modelling of frictional contact problems in static cases. This paper presents the extension of this method for dynamic analysis of impact problems with multiple deformable bodies. Instead of second order algorithms, a first order algorithm is applied for the numerical integration of the time-discretized equation of motion. The solution algorithm, named Bi-First, is simple and efficient. The principle of energy conservation for the given exemples is well preserved using the algorithm without any regularization. The numerical results also show clearly the physical energy dissipation introduced by frictional effects between the solids in contact.