Space-Time Adaptive Processing (STAP) can be used in combination with monopulse techniques for the estimation of spatial and temporal parameters of moving targets in airborne radar. However, in non-homogeneous environment, the available amount of secondary data which have the same statistical characteristics with the clutter in the primary data is very limited. In this case, the optimum STAP is impractical. In this paper, by combining linearly constrained monopulse technique with STAP, a Reduced Dimension Spatial and Temporal Parameter Estimation (referred to as RD-STPE) method is proposed. Simulation results show that, in non-homogeneous environments, the proposed method can improve the estimation accuracy of the target parameters dramatically, and is more robust than the full dimension adaptive monopulse method with STAP.