A fastening assembly includes: a first sleeve, a second sleeve, a positioning element, a driven element and an elastic element. The first sleeve includes a plug tube having a passage communicating with the first sleeve. The second sleeve is integrated into the first sleeve. The driven element includes an inserting rod movably inserted in the passage along a first direction and a guiding portion having a first inclined guiding surface forming a first acute angle with the first direction. The positioning element includes a guide rod movably inserted in the second sleeve along the second direction and a slide block connected to the guide rod and in sliding contact with the first inclined guiding surface. One end of the elastic element leans against the driven element, and the other end of the elastic element leans against the first sleeve.