Developing an eco-friendly approach for metallic nanoparticles synthesis is important in current nanotechnology research. In this study, green synthesis of gold nanoparticles(AuNPs) was carried out by a newly isolated strain Trichoderma sp. WL-Go. UV–vis spectra of Au NPs showed a surface plasmon resonance peak at 550 nm, and transmission electron microscopy images revealed that the Au NPs were of varied shape with well dispersibility.The optimal conditions for Au NPs synthesis were HAuCl_4 1.0 mmol/L, biomass 0.5 g and pH 7–11. Moreover, the bio-Au NPs could efficiently catalyze the decolorization of various azo dyes. This research provided a new microbial resource candidate for green synthesis of Au NPs and demonstrated the potential application of bio-Au NPs for azo dye decolorization. Developing this eco-friendly approach for metallic nanoparticles synthesis is important in current nanotechnology research. In this study, green synthesis of gold nanoparticles (AuNPs) was carried out by a newly isolated strain Trichoderma sp. WL-Go. UV-vis spectra of Au NPs showed a surface plasmon resonance peak at 550 nm, and transmission electron microscopy images revealed that the Au NPs were of varied shape with well dispersibility. The optimal conditions for Au NPs synthesis were HAuCl_4 1.0 mmol / L, biomass 0.5 g and pH 7- This research provides a new microbial resource candidate for green synthesis of Au NPs and demonstrated the potential application of bio-Au NPs for azo dye decolorization.