Compound staining method can solve the problem that traditional combination screening of cervical cancer can not be carried out on the same smear. In view of the problems of DNA absorbance interference and color restoration distortion caused by compound staining, a microscopic spectral imaging system with multi-band illuminants was established in this paper. The design of composite illuminants gave consideration to both the restoration of color image and the establishment of absorbance model, multi-spectral unmixing model were constructed by multiple linear regression method, and by using this modle Feulgen′s real absorbance were unmixed from the mixing muti-spectral images for DNA quantitative analysis , and pseudo color images were also composed to meet the doctors′ requirements and habits at the same time. Experimental results show that: the Full Width at Half Maximum (FWHM) of the chosed four-band illuminants were 12 nm/12 nm/14 nm/19 nm, and they were satisfactory narrowband monochromatic lights; The measured maximum offset of spot does not exceed 3 scale by using a microscope micrometer as a ruler and the original illuminant as a standard, so parallelism and coaxiality of the composite illuminants met the requirements of imaging system; The synthesis pseudo color images were bright and full , and have clean background, they will not cause interference and obstacles to doctor′s diagnosis.The absorbance unmixing model can successfully unmixing the real absorbance of feulgen and accurately calculate the content of DNA: The liver smear of mice was used as the measuring specimen and the calculated DNA index (DI) values accorded with the polyploidy of liver cells; In contrast experiments using a cervical positive sample, the DI values of the diploid and tetraploid cells calculated by the two methods were almost equal, therefore, this method has higher accuracy and reliability.