A micro-displacement measurement system is established based on transmissive laser air-wedge interference. The system realizes displacement measurement in one dimension with nanometer resolution. We use an image processing method, applying an extra small displacement and calculating the light intensity difference, to extract the interference patterns buried in stray light and noise, and effectively improve the signal-to-noise ratio of the laser interferometric images. Results show that the relative displacement resolution of the system is better than 10 nm and the absolute displacement measurement uncertainty is better than 5%. The measuring system is compact in structure, easy to install and use, and the measuring resolution reaches the nanometer level. It realizes fast, convenient and stable measurement, and is suitable for temporary demand of high resolution and precision displacement measurements.