The present invention relates to an anchor assembly and an anchor assembly forming method to support a hydraulic jack when the hydraulic jack is lifting structures or piles are being constructed. The anchor assembly according to the present invention is for a pile construction device which comprises a reaction body supported in a supporting surface and extended to the top; a fixing plate fixed to the top of the reaction body; and the hydraulic jack supported in the fixing plate to indent piles to the bottom. The anchor assembly comprises an extension rod which is extended to the bottom through the supporting surface to be adjacent to the pile insertion hole of the supporting surface to be inserted with a reinforcing pile and is connected to the reaction body; an anchor member which is installed at the bottom of the extension rod and is protruding from the extension rod in the radial direction to form a catching protrusion to prevent the extension rod from coming out to the top of the supporting surface; and a fixing part to fix the extension rod to the supporting surface. The anchor assembly and the anchor assembly forming method according to the present invention facilitate the formation of the anchor member to support the hydraulic jack.
