During the design of the electrohydraulic servovalve, if the output flow of the electrohydraulic servovalve is relatively large, the designer must consider its flow saturation problem. Through theoretical analysis, the flow function of servovalve and the theoretical linearity expression of the function which contained the saturation factors were established. These conclusions could be used as a theoretical basis to avoid or weaken the flow saturation problem in electrohydraulic servovalve design.This theory was used to optimize an existing servovalve whose output flow curve was severely saturated, a new servovalve was designed and produced. By comparing the old and the new servovalve, the application value of the theory in electrohydraulic servovalve design was verified.