This paper describes the build of a original position optic measuring system with high precision and wide scanning wavelength

which can measure feeble signal accurately buried in noise

based on virtual Lock-in technique. In this paper

we firstly introduce the aim

the structure

and the measuring principle of this system. Then we emphatically describe how to use the G language Labview to write a program to implement the virtual Lock-in technique

and how apply it in our system. This technique not only reduce the cost

but also simplify the structure of the system. After that we measured the distribution of lamp’ intensity between 200nm-2500nm; and measuring the repetition of wave band 200-860nm and wave band 860-2500nm.Finally we measure the transparence of a quartz glass

and compare with the measuring result of lambda950

the mean error is 0.95%. The results of experiment indicate that

this original position measuring system that use the virtual Lock-in technique to deal with the data

can measure well and truly

by restraining the noise brought by interferential light and electronic equipment. It is competent for original position measurement for specimens′optical character.