Abstract: This paper introduces a kind of immune colloidal gold detector instrument from the aspects of machinery,hardware and software.The instrument first collects one image through a CMOS sensor and then analyzes the image with image processing algorithm on Linux platform.Firstly,the instrument sets and stores the parameters separately for each test item,and then calls the saved item parameters when testing the item sample.So,the instrument can be used in a variety of fields and items.In this paper,a quantitative experimental test on C-reactive protein sample was performed,and the results indicate the coefficient of determination what denoted R² equal to 0.99,and the repeatability is greater than 93%.