Aim at the problem of bearing-only target tracking of mono-station measurement, a new elevation parameter estimation algorithm is proposed which is based on invariable-information of mono-station flight plane and information supported by bearing-only measurement. According to the deduced dihedral angle relation, horizontal supplementary angle and dihedral angle can be easily solved and forecasting formula of target elevation series is given by utilizing target projection course angle calculated by bearing-only series. Finally, an analysis of impact of azimuth noise on elevation error is done. The use of this method preferably solves the problem of nonlinearity of mono-station measurement and the simulation experiment shows that the estimation of invariable parameter of target movement is good in effect and the elevation prediction series are of good accuracy and precision