Abstract: In order to understand the function and safety of Penicillium chrysogenum during the fermentation process of Pu'er tea, P. chrysogenum, separated from the Pu'er tea, was inoculated on the sun-dried green tea with 35% water, for 25 days at 30℃, then the sensory, security, physical and chemical of fermented sample was evaluated. The results showed that compared with CK, the contents of tea polyphenols, soluble sugar, theabrownins, redness and brightness changed significantly in the fermented sample with sweet aroma, henna tang, velvety flavor, and the contents of citrinin and patulin were lower than the limition of home and abroad. In conclusion, P. chrysogenum is one of preponderant fungus during the fermentation process of Pu'er tea, and plays a very important role in the formation of Pu'er tea quality with high safety.