In this paper, the extruded summer and autumn green tea powder processed with a twin screw extruder, the effects of material moisture, barrel temperature and screw speed on the content of tea polyphenols in green tea powder was studied after extruding. Moreover, the leaching functional components and microstructure changes were also studied. The results showed that the moisture content of the material increased, and the content of tea polyphenols decreased first and then increased; increasing the barrel temperature could increase the leaching of tea polyphenols, while the high temperature would lead to the loss of tea polyphenols; increasing the screw speed could increase the tea powder damageand promote the leaching of tea polyphenols. However, the barrel temperature and screw speed had little effect on the puffing degree of the extrudates, and the influence of material moisture content was relatively large. Compared with unprocessed summer and autumn green tea, the tea polyphenols, crude fiber, total soluble sugar content decreased and theanine content increased in summer and autumn green tea powder processed. After the expansion of summer and autumn green tea, the surface structure was observed to be flat and smooth under a scanning electron microscope, and the mechanical force caused the cleavage of the chemical bond of the material itself.