Abstract: The theory of negative control system is analysed and a control model of this system is established. It shows that the energy saving theory of such system is to reduce the flow of bypass channel of 6 way spool valve and control such flow to a constant value. The model is validated on an experimental excavator in which the bypass pressure of the 6 way spool valve is controlled according to different setting value with the help of electrical hydraulic control technique, which successfully simulates the real hydraulic system of excavator that use negative control theory. The further application of the negative control model is also discussed.

Key words: Energy saving, Hydraulic excavator, Negative control