A card tray ejection mechanism for an electronic device, which includes a first elongated member rotatably mounted to the base, a second elongated member, and a driving member. The first elongated member includes a first end portion resisting against a side of the tray, a second end portion opposite to the first end portion and a pivoting rod located between the first and second end portions. The second elongated member is rotatably connected to the second end portion. The driving member drives the second elongated member to move longitudinally. When the second elongated member is driven to move longitudinally by the driving member, the first elongated member is driven to rotate around the pivoting rod by the second elongated member, and the card tray is ejected. An electronic device using the card tray ejection mechanism is also provided.