A screw retaining mechanism includes a hollow stud and a nut is matched with the hollow stud. The hollow stud has a plurality of elastic plates extending from a free end thereof and along a peripheral wall thereof. An opening is located between two adjacent elastic plates. An inner wall of the nut has a plurality of tubers protruding in the axial direction to match into the opening. The elastic plate defines a first side face and a second side face opposite to the first side face. Said first side face is used to guide the tubers into the opening and the second side face prevent the tuber fall off from the stud.