The present application provides a process of surface treatment of a silicon-on-insulator (SOI) wafer comprising: providing a SOI wafer comprising a back substrate, a top silicon layer and an insulating buried layer, wherein the insulating buried layer is located between the back substrate and the top silicon layer, and the top silicon layer has a surface roughness of larger than 10 Å; conducting a first planarization to a surface of the top silicon layer by conducting a batch annealing process at a first target temperature, and conducting a second planarization to a surface of the top silicon layer by conducting a rapid thermal annealing process at a second target temperature. The present application combines the batch annealing process and the rapid thermal annealing process to optimize the SOI wafer, especially the surface roughness of the SOI wafer. The SOI wafer planarized by the two thermal annealing processes has a good surface roughness of the top silicon layer which satisfies process requirements.