Grouping oil supply is a reasonable selection to hydraulic power actuating system in multi-component production line.Considering the basic requirements of grouping oil supply,loop design,oil pump selection,displacement calculation,system efficiency,design calculation of basic parameters and so on were researched.On these grounds,group forming criterion was come up with based on hydraulic system efficiency.Using the method of grouping oil supply,a successful example of hydraulic system reformation in casting production line was introduced,and the conclusion was validated.It can be used for reference in the design and reformation of hydraulic system in production line.