In this work, the non-stoichiometric surface of Al_xGa_1-xN(x=50%) subjected to ICP etching was studied by XPS (X-ray Photoelectron Spectroscopy). Under the condition of identical etching depth, the effects of ICP pressure on the surface damages of etched AlGaN were investigated, furthermore, the recovery function of low-temperature annealing to nitrogen deficiency (V_N) was evaluated. XPS tests show that serious stoichiometry disorder and nitrogen deficiency appear at the AlGaN surface after ICP process, which results in the moving to the higher bind-energy of Al2p and Ga3d peaks. This study reveals that moderate ICP pressure is needed to depress the etching damages. Also, it is confirmed that low-temperature annealing (380℃-200s) can recover the nitrogen deficiency partly, but this recovery is not effective enough.