In this paper is described a set of constraints applied to a wireless power-supply system (emitter and receiver) for operating in optimal conditions. These constraints regard both geometrical aspects and operational conditions of the system. There is also presented the performance optimization in the power wireless transfer. Starting from the equivalent scheme of a wireless power transfer system sinusoidal behavior, there are generated the system performances (the delivered active power or the system efficiency) in full symbolic and/or symbolic-numeric forms, obtaining an appropriate frequency space representation based on the complex or Laplace modified nodal equations (MNE) or/and Laplace state variable equations (SVE). In order to obtain the optimal values of the system parameters, that provide the maximum performances, there are used the MATLAB procedures which minimize these objective functions. These equations are combined with some measurements performed on the real system and an unconstrained minimization algorithm for some scalar and/or vector functions of multiple variables provided by MATLAB Optimization Toolbox. The algorithm is suitable to compute optimal circuit parameters, which guarantee the minimum and maximum values of the performance quantity. Linear or small-signal nonlinear circuits can be treated in this manner. This study has also highlighted some aspects regarding the conditions that have to be accomplished by a power supply system that uses wireless technologies, for an optimal transfer of energy. The proposed optimization techniques were tested and validated with simulation data on some illustrative examples.