A guardrail post comprising: - a post body; - a first sleeve secured to the post body; - a locking mechanism, characterized in that the locking mechanism comprises:. a locking tube having an end extending inside the first sleeve, the locking tube defining a plurality of spaced arranged first through holes at the other end thereof along a peripheral sidewall;. a plurality of clamping pieces positioned in the plurality of first through holes, respectively, and. a locking sleeve sleeved on the locking tube and having an inner sidewall defining an inclined surface, the inner sidewall engaging with the plurality of clamping pieces; and in that the guardrail post further comprises: - a second sleeve having a bottom end extending inside the locking sleeve, the second sleeve defining a first notch extending along an axial direction at a top end thereof; - a slider slidably received in the second sleeve, a top end of the slider forming two protrusion plates spaced from each other, each protrusion plate defining a second through hole; - a first fastener; - a limiting seal cover positioned on the top end of the second sleeve, the limiting seal cover defining a second notch along an axial direction at a top end, the limiting seal cover forming a blocking wall protruding inwardly along a radial direction at the top end; and - a first hanging rod extending inside the limiting seal cover, the first hanging rod defining a third through hole at an end; wherein the first fastener extends through the third through hole, and opposite ends of the first fastener extends inside the two second through holes, respectively. - a post body; - a first sleeve secured to the post body; - a locking mechanism, characterized in that the locking mechanism comprises:. a locking tube having an end extending inside the first sleeve, the locking tube defining a plurality of spaced arranged first through holes at the other end thereof along a peripheral sidewall;. a plurality of clamping pieces positioned in the plurality of first through holes, respectively, and. a locking sleeve sleeved on the locking tube and having an inner sidewall defining an inclined surface, the inner sidewall engaging with the plurality of clamping pieces; and in that the guardrail post further comprises:. a locking tube having an end extending inside the first sleeve, the locking tube defining a plurality of spaced arranged first through holes at the other end thereof along a peripheral sidewall;. a plurality of clamping pieces positioned in the plurality of first through holes, respectively, and. a locking sleeve sleeved on the locking tube and having an inner sidewall defining an inclined surface, the inner sidewall engaging with the plurality of clamping pieces; - a second sleeve having a bottom end extending inside the locking sleeve, the second sleeve defining a first notch extending along an axial direction at a top end thereof; - a slider slidably received in the second sleeve, a top end of the slider forming two protrusion plates spaced from each other, each protrusion plate defining a second through hole; - a first fastener; - a limiting seal cover positioned on the top end of the second sleeve, the limiting seal cover defining a second notch along an axial direction at a top end, the limiting seal cover forming a blocking wall protruding inwardly along a radial direction at the top end; and - a first hanging rod extending inside the limiting seal cover, the first hanging rod defining a third through hole at an end;