Palladium nanoparticles (bio-Pd) were synthesized by Staphylococcus sp. JJ-1 and applied to the catalytic reduction of methyl green in situ. Characterization by transmission electron microscopy (TEM),X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) showed that zero-valent Pd were synthesized. Bio-Pd mainly distributed on the outer surface of cells，and their average diameter was about 15-40 nm with well crystal structure. Synthesized Bio-Pd was used to reduce methyl green and removed 99% of dosed methyl green in 1.5 hours. The products of methyl green reduction were analyzed by ultraviolet-visible absorption spectroscopy (UV-visible) and liquid chromatography-mass spectrometry (LC-MS). Main products were 4-(N，N-dimethylamino)-4'-(N'，N'-dimethyl Amino) benzophenone (DDBP) and 4-(N-ethyl-N，N-dimethylamino)-4'-(N'，N'-dimethylamino)benzophenone (ED- DBP).The results showed that Staphylococcus sp. JJ-1 synthesized palladium nanoparticles and efficiently reduced methyl green.