Autocoupling is a special operation mode of power transformers.It saves materials by sharing a part of coils with input and output to meet highefficiency energy transmission under variable voltage demand.In the field of hydraulic transmission,the cylindertype hydraulic transformer can also adopt the “autocoupling” operation mode,which expands the range of the transformation ratio through the input and output sharing part of the piston area,so that the hydraulic potential energy transmission is more efficient.The concept of autocoupling in the field of hydraulics was introduced.The autocoupling operation mode of the cylindertype hydraulic transformer device for hydraulic potential energy transmission was realized.According to theoretical analysis and simulation calculation,the addition of the autocoupling mode increases the number of transformation ratios compared with the normal operation mode.Under the requirement of fixed transformation ratio,the design requires a smaller piston area to save cost and space.And when the multistage hydraulic cylinder is used in combination,the addition of the autocoupling operation mode realizes more hydraulic potential energy conversion with different proportions,the utilization of the piston area is improved greatly.