Electro-hydraulic actuators are used for proportional regulation of the flow of mobile valves with high capacities. Mobile hydraulic valves are used because of their simplicity and relatively low price increases. Frequency of use also causes errors which must be detected and, if possible, eliminated. The operation of valve depends on several factors, one of the most important is proper functioning of the electro-hydraulic actuator. The research consists of a theoretical part in which the digital hydraulics and a detailed description of the operation of actuator are presented. With the help of dismantling and reconstruction of the considered actuator, its structure and operation are described in more detail. Results of the reconstruction are presented with a picture, and a detailed understanding of the actuator's operation was helpful in designing the test station.