Acording to the Jones matrix,the intelligent system for measuring retardation of wave plate has been designed and established and the automatic processing of the data was realized,based on the polarization modulation and use of advanced Si detector,lock-in amplifier and advanced microprocessor technology.The rotation angle was controled by the feedback loop system.The purpose of this project is to improve the automatic degree and measurement accuracy,and to enlarge measurement range.The system has the features of high precision,good repeatability,high automatic degree and simple operation.The measurement result indicates that the measurement range is from 400 nm to 1 000 nm,the measurement accuracy excels 0.1 percent,the repetitive error is less than 0.6 percent.So this measurement system can be widely used in polarization area.