Abstract: An anti-loosening endcap for utility crossarm comprising an endcap body inserted into the crossarm, where a channel perpendicular to an inner wall of the crossarm is disposed inside the endcap body, one end of the channel is open, the pointed head pin is slidably disposed in the channel, the pointed head of the pointed head pin faces the inner wall of the crossarm, the endcap is further provided with an axial through passage, the passage and the channel intersect at the tail portion of the pointed head pin, and the corresponding pin is provided for the passage. The pin is driven into the passage, and the pin presses the tail portion of the pointed head pin, so that the pointed head of the pointed head pin pierces the inner wall of the crossarm, thereby providing a locking effect.