Abstract: According to the conversion formula between the normal topocentric and vertical topocentric coordinate system, Observation equations with observations such as horizontal direction, vertical angle and distance of ground network in space-rectangular coordinate system are listed when considering the vertical deflection component as unknown parameters. Parameter estimation and precision evaluation formula of combined adjustment of GNSS network and terrestrial network with additional vertical deflection are deduced. The vertical deflection is solved using real data of GNSS observations as well as the Terrestrial network. The results show that the new approach can eliminate the influence of vertical deflection to the observations when considering the vertical deflection component as unknown parameters, thus this approach can remarkably improve the calculating precision and reliability of the unknown point coordinates.