Annotation: In the article the theoretical basic concepts of the substantiation of the optimum measuring signals synthesis criteria for control of parameters of systems and elements of complex radio engineering systems (including unmanned and manned aircraft, samples of guided missile armament, radar stations, etc.) are proposed and studied. The analysis of known methods of controlling the technical state of complex radio engineering systems based on the investigation of their dynamic characteristics has been carried out. The results of such analysis allow achieving the goal – to substantiate the criteria for calculating the parameters of the optimal input measuring signal for controlling the technical state of complex radio engineering systems. It is shown that with a sufficiently small impedance of the input signal, practically all measuring signals are equivalent. Therefore, the task of selecting the parameters of an optimal measuring signal is relevant only for a rather large obstacle. The main criteria of optimization of parameters of incoming measurement signals, which include the maximum of the information index, the minimum of the mean square error, the maximum of sensitivity are considered. It is substantiated that the criteria considered are reduced to the one that is proposed to be used to find the parameters of the optimal input measurement signal used to control the technical state of systems and elements of complex radio systems at the exploitation stage.