The pitch bearing is a component in wind turbine units used to adjust the angle of the fan blades to adapt to the wind direction, so as to maximize the utilization of wind energy. Due to the different working mode of the pitch bearing itself compared with ordinary small bearings and the harsh working environment, the pitch bearing is prone to faults such as cracking and deformation. In severe cases, it will lead to overall damage to the pitch bearing, causing the blade to fall from a high altitude and even injuring personnel. Therefore, this paper conducts a patent analysis and technical decomposition of the deformation monitoring device for pitch bearings, analyzes and summarizes the development process of existing deformation monitoring devices for pitch bearings. Combined with the TRIZ evolution theory and based on the S-curve, it is concluded that the current deformation monitoring device for pitch bearings is in the transitional stage between the infant period and the growth period, and discusses the possible subsequent evolution directions. Through reviewing relevant literature, it is found that inner ring cracks first appear near the upper and lower surfaces of the bolt holes in the inner ring of the pitch bearing. To this end, a new type of deformation monitoring device for pitch bearings is designed. The fiber optic displacement sensor is used for qualitative monitoring of initial cracks near the surface of the bolt holes in the inner ring of the pitch bearing. After cracks are detected, the eddy current sensor is used for quantitative monitoring of whether there are extended cracks between the cracked bolt holes and adjacent bolt holes. Finally, the work done in this paper is summarized and prospected.