During the course of designing the hydraulic control system of the boom,which is the largest domestic quality 270 t large hydraulic excavators,multi-pump(four pumps) for oil and incorporation outside the valve are adopted to meet speed requirements while the boom is uplifting.While the boom is declining,the weight of mechanical components and large inertia of declining lead to great pressure shocks at the last stage of declining,low declining speed and low efficiency.In order to solve the problem,flow regeneration circuit is adopted to realize energy recycle,reduce the pressure shock and make the speed faster through the use of regeneration valve and so improve the efficiency.The experimental research of the excavator indicates that the designed hydraulic control system with maximum test load 25 t can fully meet pressure and speed the boom needed at its normal work.The boom can be fully declined in place after flow regeneration circuit is adopted with the declining time shortened from 37 s to 18 s,speed clearly accelerated,pressure more stable,and no apparent hydraulic shock.At the same time the system energy consumption is reduced without hydraulic pump for oil supply.Through the test,the correctness of the hydraulic control system of the excavator gets verified.And importantly data and experience have been accumulated for the future design and manufacture of larger hydraulic excavators.