Lithium niobate (LiNbO3, LN) is a widely used dielectric material. Because of its large electro-optical coefficient, large transparent range and wide eigenband, it is extremely important in integrated and nonlinear optical devices. However, due to the good chemical stability and slow etching rate of lithium niobate on insulator (LNOI), the microstructure parameters are difficult to control. In view of the abovementioned problems, the preparation process of LNOI ridge microstructures based on inductively coupled plasma etching (ICP-RIE) was studied in this paper. The effects of chamber pressure, total gas flow and etching power on the etching rate, etching angle and surface roughness (RMS) were analyzed. The research shows that under the optimized process conditions, the etching rate of LNOI reaches 24.9 nm/min, and the LNOI ridge microstructure with etching depth of 249 nm, etching angle of 76 ° and surface roughness (RMS) of 0.716 nm is prepared. Through the study of etching process and microstructure parameters, this paper creates a LNOI microstructure etching method based on ICP, which provides technological support for controlling the LNOI ridge optical waveguide and improving its performance.