In order to realize high-precision real-time detection of large-stroke precision optical focusing components In order to realize high-precision real-time detection of large-stroke precision optical focusing components, high-precision long-displacement sensors based on axial eddy current effect are studied. A long-displacement eddy current probe simulation model is established for linearity testing, an eddy current sensor test system is built for accuracy experiments, and the long-displacement eddy current sensor is connected to the precision optical focusing assembly. The experimental results show that while the measurable displacement reaches 24mm, the linearity is better than 1%, the resolution is better than 0.5um, the accuracy is better than 1um, and the high-precision long-displacement eddy current sensor meets the requirements of the precision optical focusing assembly.