Adult blood with silver nanoparticles is radiated by laser with wavelength of 407 nm, and the effect of colloidal silver nanoparticles on the fluorescence performance of zinc porphyrin (ZPP) in blood has been investigated. It has been found that colloidal silver nanoparticles can enhance fluorescence intensity of ZPP in low concentration human blood significantly, the highest enhancement ratio is about 5.2. Moreover, with the increase in silver colloid amount, the fluorescence enhancement efficiency increases firstly and then decreases. Theoretical analysis indicates that when the distance between ZPP molecules and silver nanoparticles in the solution meets fluorescence enhancement condition, the intensity of ZPP fluorescence can be improved. However, after adding extra silver particles, the distance between molecules will decrease, which is detrimental to the enhancement effect. The research shows that silver nanoparticles can enhance the fluorescence intensity of ZPP in low concentration human blood, which is important for the improvement of ZPP detection sensitivity and accuracy.