The effect of interparticle potential on the sedimentation of a colloid system has not been solved completely. A key problem is how to deal with the interparticle potential in stable systems. Based on previous works, an interparticle potential function for a stable system that cuts off the potential interaction at the position of the potential barrier (the position where interparticle potential is equal to 15 kT) is presented. Adopting this potential function, the sedimentation coefficients of monodisperse systems containing potential interacting particles are calculated, and the theoretical results are compared with those given by experiments. The potential function for the adopted stable system is more useful and reasonable than previous ones.