In this work, the structural transitions of ZnO and SnO2 nanowires (NWs) in high current density operation can be observed. The structure of ZnO and SnO2 NWs will change from the single crystalline to the poly crystalline or the amorphous structure. The structural transition process is due to the joule heating effect by operating the nanodevice in high current density. From this research work, we can study the structural transition by tuning the current density; and about the 7.9x107 A/m2, the structure of NWs would be changed.