The electronic structure of the clean AlN surface and the ultrathin K/AlN interface has been studied in situ by synchrotron-based photoelectron spectroscopy using the photon energies in the range of 100-650 eV. The effect of K adsorption was studied. Changes in the valence band and in the Al 2p, N 1s, and K 3p core levels spectra have been investigated using K submonolayer deposition. Modification of the surface electronic structure of the AlN caused by K adsorption is found to originate from the local interaction of N surface atoms and K adatoms. As a results the suppression of intrinsic surface state and appearance of a new induced state are observed. It was found the K-induced electron redistribution effect that causes the positive energy shift of N 1s surface peak and increasing N-ionicity. Keywords: III-nitrides, electronic structure, surface states, metal-III-nitride interfaces, photoelectron spectroscopy.