The XPS, oxygen content and resistance-temperature relationship of YBa2Cu3-xAlxO7-y single phase system are determined. The experimental results show that Al can possibly substitute the Cu and Y positions in 1-2-3-phase partially. Because of the existence of Al3+, the content of oxygen increases, the environment of oxygen tends to be uniform, the difference of the two states of O15 in XPS is indistinct. The presence of Cu3+ is clearly observed.