Abstract: With the development of semiconductor industry,the critical dimension of integrated optoelectronic devices are becoming smaller and smaller, the technology of smoothing nano optical waveguide surface are facing new challengs. Reducing the nano optical waveguide surface roughness, manufacturing ultra-low loss nano optical waveguide and achieving the efficient optical interconnection and inside coupling between chips are the key to optoelectronic devices integration and especially the development of high sensitive micro gyro, biochemical sensors, optical communication devices and so on. In this review, the relationship between surface roughness and scattering loss were analyzed while the emphasis was the technological approaches of smoothing nano optical waveguide surface, including the research status and the latest achievements of thermal oxidation method, hydrogen annealing method and laser reformation method. Additionally, the technical difficulties and development prospects of various technologies were summarized together with their application prospects in the fields of MEMS, large-scale photonic integrated circuits.