An in-depth understanding of the formation of silicon dioxide (SiO2) on silicon carbide (SiC) in thermal oxidation is imperative for micro/nano fabrication processes, integration of electronic components, and evaluation of SiC device performance under extreme conditions. Herein, we report a comprehensive study on the effects of crystalline orientations, thicknesses, and growth temperatures of cubic SiC films on their wet oxidation properties. The oxidation rate and surface morphology were characterized using atomic force microscopy (AFM) and light reflectance measurement systems. Our experimental results revealed the role of defects in the SiC crystal on the oxidation that relates to SiC thickness, deposition conditions, crystal orientation and temperature of wet oxidation. Critically, the electrical properties of SiC films oxidized at 900 °C remained the same as the unoxidized film as confirmed by room-temperature current-voltage measurements, indicating a long-term service temperature of SiC. These findings are expected to provide crucial information on the effects of defects on the formation of SiO2 on SiC films at different oxidation temperatures, which is highly essential for establishing a basic platform for the fabrication of high-performance SiC-based electronic devices.