An improved disposable puncture depth adjustable safety lancet consists of a shell, a lancet core, a spring and a trigger； wherein: the shell is provided with an adjusting ring to adjust the puncture depth in the front end； the adjusting ring is sleeved clearance-fit at the outside of the trigger head； the adjusting ring and the shell are connected in a rotational way in the peripheral direction, and are connected in a fixed way in the axial direction, and a rotational locating structure is set between the adjusting ring and the shell in the rotation direction； the adjusting ring is equipped with the rotating step face or rotating bevel on the inner wall, and rotate the adjusting ring to be in the different locating positions and the rotating step face or rotating bevel meets the collision face of lancet core in the different axial positions, thereby changing the puncture depth of needle tip. The present invention changes the original way of connecting the adjusting component to the trigger to the way of connecting the adjusting component to the shell, therefore the false triggering will not be caused as the rotation of the adjusting component is irrelevant to the trigger. The present invention essentially and fundamentally solves the problem of product waste caused by the false triggering prone to happen during the rotation of adjusting head before.
