Blood plays an important role in the clinical diagnosis and treatment; many diseases may lead to changes in the blood composition or characteristic properties. Therefore, the analysis of blood sugar will be of great importance. The present paper studies the difference of fluorescence intensity stimulated by light wave between normal blood serum and hyperglycemia blood serum. The result shows that the average grey level of fluorescence image at 365 nm increases obviously with the changes in the concentration of glucose; however, the average grey changes little at 353, 369 and 405 nm. This shows that the main effect of serum glucose on the fluorescence intensity peak appears at 365 nm. Because the fluorescence intensity has something to do with the concentration of the fluorescence material, the blood glucose concentration influences directly the fluorescence intensity at 365 nm. Therefore, it is possible to judge blood sugar content, and to make sure whether the content exceeds the normal value or not by comparing the fluorescence intensity of the blood serum measured at 365 nm. This technique of optical measurement provides an experimental basis for the diagnosis of blood diseases.