This paper presents a new model of the steady state analysis of variable displacement hydraulic pump which is called the invariable pressure and invariable flow model. By the new model, a variable displacement hydraulic pump is simulated by the ordinary hydraulic component with hydraulic resistance, abrupt pressure change and invariable flow. The variable displacement hydraulic pump exists as an ordinary hydraulic component in the system and needn't to be simplified as a boundary point when a system model is established in analyzing the steady state characteristic of a hydraulic system.