Silicon photonic mode size converter is the key device for silicon based photonic integrated chip to connect with external optical fiber, it plays an important role in integrated optical path. The mode size of the standard fibers does not match the mode size of the nanometer photonic waveguide, so there is a great coupling loss between the standard fiber and the nanometer silicon waveguide, the silicon photonic mode size converters can significantly reduce the optical loss between them. One end of the silicon based photonic mode size converter has a large mode size that matches with the mode size of the standard fiber; the other end has a smaller mode size, which can be matched with the mode size of nano-silicon photonic waveguide, thereby significantly reducing the optical connection loss between the standard fiber and the nano-silicon photonic waveguide. The characteristics of different structures of converters are reviewed, while the advantages and disadvantages of different types of converters in structure, performance and application are compared and analyzed, and the prospect of silicon photonic mode size converters is prospected and some opinions are put forward.