Based on the result of the YBCO's experiments at high temperatures, this paper analysed and discussed the Influences of oxygen on the YBCO's conduction behavior at high temperature and the conductive actions of one dimensional Cu-O chains. We also reported a new phenomenon of YBCO in N2, i.e., once the N2 atmosphere is replaced by the O2 atmosphere at high temperature, a rapid stractural phase transition from semconductor to metal will occur.