The content of air bubble in oil will effect on the value of volume elasticity modulus and the pressure of oil in working cavity of vane pump, and effect on the force of vane. The model between the air bubble content and the oil pressure in sealed working cavity is built when vane moving from big arc area to outlet area. And the equations of vane force in outlet area of vane pump are listed, and the variation curves are obtained by computer simulation when the content of air is given different value. The curve indicated the content of air bubble only effect on the value of vane force in pressure rising area of vane pump. The value of force reduced and the gradient of variation curve increased with the value of the air bubble content increasing.