Space-Time Adaptive Processing with sum and difference beams(ΣΔ-STAP) is utilized in airborne radar. It can suppress one jamming from common side lobe direction and main lobe direction well. But the effect in suppressing jamming from the beam’s zero side lobe direction is not very good and the main lobe will be separated. According to the characteristics of airborne radar, an improved ΣΔ-STAP method based on Σ, ΔA and guard channels is proposed. Simulation results present that the improved method can suppress jamming from the beam’s zero side, and the improvement factor is enhanced by 10 dB. The influence on the performance by error becomes weaker.