Abstract: A novel space time adaptive monopulse direction finding technique is proposed in this paper for airbrone phased array radar,which exhibits high accuracy performance and is robust when random array element errors(gain and phase) and channel mismatch errors exits. A robust gain normalization method for adaptive sum and difference beams is also given, together with the simplified compatible realization schemes for the above method. Finally, some results based on high fidelity simulated radar clutter data are provided for illustration.