The interaction of Ag( I ) and Phycocyanin(PC for short) was investigated by ultraviolet-visible, fluorescence and infrared spectra under the condition of 4 degrees C and without light. The results showed that the characteristic absorption of PC at 615 nm decreased gradually with the increase in Ag( I ) concentration and interaction time. Accordingly, its fluorescence emission peak and two fluorescence excitation peaks also decreased. Dynamic formation of nano-Ag(0) was also observed by synchronous fluorescence spectra, showing that Ag(0) was formed by the PC in situ reduction. It was observed by TEM that Ag(0) dispersed in PC, which formed a bioconjugate with PC as the core and nano-Ag(0) as the crust. The bioconjugate was round and its diameter was about 15-30 nm.