Poly-Si on oxide (POLO) structure is a passivation contact structure formed by growing a polysilicon layer on an extremely thin interface oxide layer based on the surface of the crystalline silicon. The passivation contact technology based on the POLO structure can not only obtain excellent surface passivation characteristics, but also avoid direct contact between the metal and the crystalline silicon surface, and greatly reduce the contact recombination of the metal and the crystalline silicon surface. At present, the conversion efficiency of small-area crystalline silicon solar cells made with POLO passivation contact structure is as high as 26.1%, and the industrialization efficiency of large-area crystalline silicon solar cells has exceeded 24.5%. At the same time, the POLO passivation contact technology applied to the production of crystalline silicon cells can withstand high-temperature processes and is compatible with existing crystalline silicon cell industrialization equipment. It is a passivation contact technology solution with great industrialization potential in the future. This paper mainly reviews the carrier transport mechanism in the POLO passivation contact structure and the corresponding quantitative parameter characterization methods. The methods of interfacial oxide layer growth, polysilicon layer deposition, doping and hydrogenation treatment in the preparation of POLO structure are compared. The parasitic absorption effect of the polysilicon layer, the morphological structure of the crystalline silicon surface, and the influence of the doping concentration distribution on the passivation contact characteristics of the POLO structure are summarized. The research progress of the POLO passivation contact technology and the difficulties in POLO solar cells production are briefly described.