An auto-retractable blood collection needle, including: a needle holder (1) including a first tube (11), a second tube (12) and a holder tail (13)； a needle (2) installed in the first tube (11)； a built-in sliding sleeve (3) which is elongated and through and has a C-shaped cross section； a needle shield (4) which is hollow and elongated； and a spring (not shown) sheathed on the first tube (11). The second tube (12) is installed in the built-in sliding sleeve (3) and is capable of sliding back and forth. The built-in sliding sleeve (3) is installed in the needle shield (4) and is capable of sliding back and forth. A locking mechanism is formed by the holder tail (13) and the needle shield (4). When the holder tail (13) is unlocked from the needle shield (4), a force of the spring pushes the second tube (12) to slide backward, and then the built-in sliding sleeve(3) is driven to slide rearward to lock with the needle shield, so that the needle is fully retracted into the needle shield. The auto-retractable blood collection needle of the present invention can prevent needle stick injuries and cross infections, reduce the damages of the needle to vessels of patients, and miniaturize product designs.
