A blood lancet, comprising: an outer sleeve, provided with a lancet outlet at one end and an accommodating port at the other end, wherein a lancet core guide portion is arranged in the outer sleeve; an inner sleeve, wherein one end of the inner sleeve enters the outer sleeve from the accommodating port, and the other end of the inner sleeve is located at the outside of the accommodating port; a lancet core, provided with a lancet body, wherein the lancet core is arranged at one end of the inner sleeve so as to rotate along the circumferential direction with the inner sleeve; and a spring, arranged between the lancet core and the inner sleeve, and provides power for the lancet core to move axially along the lancet core guide portion toward the lancet outlet, wherein: based on the axial movement of the inner sleeve in the direction toward the lancet outlet, the inner sleeve rotates relative to the outer sleeve from a first circumferential position to a second circumferential position; at the first circumferential position, the outer sleeve abuts against the lancet core to prevent the lancet core from launching, and at the second circumferential position, the lancet core is suitable for entering the lancet core guide portion for launching; and a first protrusion is arranged on the radial outer side of a cylinder body of the inner sleeve, a first blocking portion is arranged in the outer sleeve, when the inner sleeve is at the first circumferential position, the first protrusion is located on one side of the first blocking portion in the circumferential direction; and when the inner sleeve is at the second circumferential position, the first protrusion is located on the other side of the first blocking portion in the circumferential direction, and the first blocking portion prevents the first protrusion located on the other side of the first blocking portion from moving circumferentially to the one side of the first blocking portion. an outer sleeve, provided with a lancet outlet at one end and an accommodating port at the other end, wherein a lancet core guide portion is arranged in the outer sleeve; an inner sleeve, wherein one end of the inner sleeve enters the outer sleeve from the accommodating port, and the other end of the inner sleeve is located at the outside of the accommodating port; a lancet core, provided with a lancet body, wherein the lancet core is arranged at one end of the inner sleeve so as to rotate along the circumferential direction with the inner sleeve; and a spring, arranged between the lancet core and the inner sleeve, and provides power for the lancet core to move axially along the lancet core guide portion toward the lancet outlet, wherein: based on the axial movement of the inner sleeve in the direction toward the lancet outlet, the inner sleeve rotates relative to the outer sleeve from a first circumferential position to a second circumferential position; at the first circumferential position, the outer sleeve abuts against the lancet core to prevent the lancet core from launching, and at the second circumferential position, the lancet core is suitable for entering the lancet core guide portion for launching; and a first protrusion is arranged on the radial outer side of a cylinder body of the inner sleeve, a first blocking portion is arranged in the outer sleeve, when the inner sleeve is at the first circumferential position, the first protrusion is located on one side of the first blocking portion in the circumferential direction; and when the inner sleeve is at the second circumferential position, the first protrusion is located on the other side of the first blocking portion in the circumferential direction, and the first blocking portion prevents the first protrusion located on the other side of the first blocking portion from moving circumferentially to the one side of the first blocking portion. based on the axial movement of the inner sleeve in the direction toward the lancet outlet, the inner sleeve rotates relative to the outer sleeve from a first circumferential position to a second circumferential position; at the first circumferential position, the outer sleeve abuts against the lancet core to prevent the lancet core from launching, and at the second circumferential position, the lancet core is suitable for entering the lancet core guide portion for launching; and a first protrusion is arranged on the radial outer side of a cylinder body of the inner sleeve, a first blocking portion is arranged in the outer sleeve, when the inner sleeve is at the first circumferential position, the first protrusion is located on one side of the first blocking portion in the circumferential direction; and when the inner sleeve is at the second circumferential position, the first protrusion is located on the other side of the first blocking portion in the circumferential direction, and the first blocking portion prevents the first protrusion located on the other side of the first blocking portion from moving circumferentially to the one side of the first blocking portion.