The cellular redox states directly affect cell proliferation, differentiation and apoptosis, and the redox states changes is particularly important to the regulation of cell survival or death. Thioredoxin is a kind of oxidation regulatory protein which is widely exists in organisms, and the change of redox states is also an important process in redox regulation. In this work, we have used the site-directed mutagenesis of protein, SDS-polyacrylamide gel electrophoresis fluorescence spectroscopy and circular dichroism etc., to investigate redox states changes between TRX (E. coli) and glutathione peroxidase(GPX3) during their interaction. By observing the fluorescence spectra of TRX and its mutants, we have studied the protein interactions as well as the redox states switching between oxidation state TRX and the reduced state GPX3. The results demonstrate the presence of interactions and electron exchanges occurring between reduced GPX3 and oxidized TRX, which is of significance for revealing the physical and chemical mechanism of TRX in intracellular signal transduction.