Biological synthesis of gold nanoparticles (AuNPs) has attracted more and more attention due to its advantages of mild conditions,low cost and environment-friendly nature.In the present study,biosynthesis of gold nanoparticles (AuNPs) by the cell-free extracts of a fungus Trichoderma sp.WL-Go was reported.The as-synthesized particles were characterized by UV-vis spectroscopy,transmission electron microscopy (TEM).The effects of different parameters on AuNPs biosynthesis were investigated and cell-free extract concentration of 90 mg/L and reacting for 7 days were demonstrated to be suitable for AuNPs synthesis.The AuNPs were sphere shapes,with size range of 1-24 nm and an average size of 9.8 nm.The as-synthesized AuNPs were demonstrated to have good catalytic activities for the reduction of nitro-aromatics (2-Nitrophenol,3-Nitrophenol,4-Nitrophenol,2-Nitroaniline,3-Nitroaniline) with the catalytic rate constants of 7.4×10-3 s-1,10.3×10-3 s-1,4.9×10-3 s-1,5.8×10-3 s-1,15.0×10-3 s-1,respectively.Meanwhile,in decolorization of azo dyes,the AuNPs showed excellent catalytic performance with the decolorization rate of 82.2%-97.5%.The assynthesized AuNPs with small diameter exhibited great potentiality in catalysis and decolorization,which giving AuNPs much value of application.