In order to measure the changes of optic characteristics for spacial materials before and after space radiation,a in situ optic measuring system with high precision and wide scanning wavelength was designed to measure feeble signal accurately buried in noise based on a virtual lock-in technique.The system structure,and measuring principle were introduced.Then,the G language Labview was used to develop a program to implement the virtual lock-in technique,and apply it in the system.After that,the light source intensity distribution and the system measuring repetitiveness were measured.Finally,proposed system was used to measure the transparence of a quartz glass.Compared with that of lambda950,the measured results show that the mean error between them is 0.95%.The experimental results indicate that the virtual lock-in technique not only restrains effectively the noise brought by interferential light and electronic equipment,but also simplifies the system structure;This in-situ measuring system by using such technique can accurately measure optic characteristics of spacial materials.