Abstract: The hydroelectric units have to increase capacity extension due to efficiency reduction, insulation reduction and other reasons. while they are closely relate to the hydraulic equipment, The dynamic moment of the unit changes after capacity extension, The actuator,governor,oil pressure devices and other equipment of the hydraulic equipment should meet this change. Analyse the parameter calculation and systematic design, The unit's calculation of regulative guarantee requirements also changed, Which is relate to the hydraulic equipment, The effect of inertia and closed in steps on calculation of regulative guarantee is explaine. The grid also has new requirements for the performance of the hydraulic equipment to the capacity extension unit. Illustrate the working principles,design requirements,calculation method. which are mainly applied in mechanical calculation to analyse the parameters and performance of the equipment, The hydraulic equipment is the key and important equipment of hydroelectric unit, At the same time, The hydraulic equipment is also the response to the capacity and efficiency of the capacity extension unit and the guarantee of long-term operation reliability and regulation performance.