The hydraulic equipments has a high utilization in the many works such as the excavation, planation and crane works in the construction sites. They are an essential equipments in the construction site and the loading & unloading works of the large size objects. In the many parts which are composed of the hydraulic equipments, the main control valve(MCV) is the core of the equipments. The hydraulic energy from the pump controls the direction and the rate of flow and supply the pressure energy to the some actuators by MCV. In spite of the domestically producing of the common control valves, the MCV which used to the domestic equipments is imported the whole quantity. In this study, it is to reverse-engineer the MCV as the first step in the development of the MCV. To analyze the notch of the spool and the flow path and to apply the formula technique, we try to realize the optimal modeling of the MCV.