The relationship of the resistivity versus synthesizing temperature of sol-gel YBa2Cu3O7-x samples, with Tc 91K, was studied while synthesizing in flowing oxygen atmosphere. A set of high temperature -T curves were obtained for the whole process. After four rounds of synthesizing, the resistivity of the sample was =1.00×10-3cm at room temperature. The -T curve of the last round also showed that the orthorhombic to tetragonal phase transformation of the sample occurred around 600oC that is lower than the YBa2Cu3O7-x sample prepared in ambient atmosphere. Other measurements such as X-ray diffraction, SEM measurement, low temperature R-T and M-T measurement were also taken to get more information of these samples.