In order to detect the peak height and average wave spacing of the packing board , a size measurement system based on line structured light is proposed. Firstly , the composition of the system and the measurement scheme based on the laser triangle method were introduced , calibrated the measurement system , obtained the coordinate con- version relationship between the camera imaging model and the measured object. Then , extracted the center of the line laser stripe by the improved gray-gravity method. Finally , the collected point cloud data was sliced along the y-axis to fit points on multiple sections to complete peak height and average wave spacing measurement. The experimental re- sults show that the improved light bar center extraction method has higher accuracy , the measurement error of peak height can reach ± 0. 04 mm , and the measurement error of average wave spacing can reach ±0. 08 mm , which meets the actual production needs.