This paper presents a global characterization and an analytical model of the static flow stage of an electro-pneumatic proportional valve FESTO MPYE-5-M5-010-B. This study is useful for linear or nonlinear control synthesis in our application for medical robotics. Firstly, the experimental measurements are carried out using 3D graphs where a set of curves gives the output mass flow rate as a function of the electrical input of the electronic stage for different values of the output pressure. The exhaust and supply pressures, during these tests, are assumed to be constant. Moreover, 2D classical curves given by some constructors can be reconstructed, such as mass flow gain, pressure gain and mass flow characterization. Secondly, an approximation of the mass flow stage characteristics of this five-way proportional valve by a polynomial function is described. The model elaborated enables a good reproduction of the pressure gain and the global mass flow characterization curves to be obtained.