A pre-step co-simulation method and device for co-simulation of several subsystems is disclosed, utilizing partial derivatives of replacement subsystems. On this basis, the exact solutions of output variables of the individual subsystems are approximated by evaluation of an Error Differential Equation in order to estimate the future progress of the approximated exact output variables; corresponding input variables are determined by optimization prior to the current co-simulation time increment. The pre-step co-simulation method is realized within a computer-executable program and implemented in a network of computing nodes.