We have studied the AlOx-Al tunneling barrier in Josephson junctions by measuring XPS, AVS and Fiske step voltage.From these measurements we have found that the minimal optimum deposition Al layer thickness is 7nm in the tunneling barrier of junction that the thickness of the AlOx formed on Al only depends on oxidation condition and that the Al oxide in the tunneling barrier structure can contain an OH radical as AlOOH state.Also we evaluated the remnant Al thickness,and confirmed that the proximity effect generated by normal Al between the AlOx and low Nb exists.