The crystal structure, electronic transport properties in normal states, and superconductivity of a series of sample YBa2Cu3-xMxO7-y, (M = Zn,Ni, 0≤x≤0.3) have been studied, and a more direct evidence of preferential substitution of Zn for Cu(2) is obtained. In addition, an orthor-hombic(Ⅰ)-to-orthorhmbic(Ⅱ) structural transition in Zn-doped system as well as the effect of electronic localization in Ni-doped system is observed. The investigation shows that the Zn2+ may replace Cu(2) preferentially, but no such replacement for Cu by Ni was found. The role of Cu-O planes and chains on superconductivity is discussed. The importance of the coupling between Cu-O sheets and chains for high Tc superconductivity are noticed.