The invention relates to the technical field of architectural engineering, and especially relates to a friction pile and a construction method thereof, in particular to a large-diameter super-long friction pile capable of fully achieving friction force of an upper side and a lower side of a foundation pile and end resistance of the foundation pile. The friction pile comprises an upper pile body, a lower pile body and a separation formwork arranged between the upper pile body and the lower pile body. An annular bevel body is arranged at the bottom of the upper pile body, and the lower pile body comprises a force transferring structural segment, a variable-section structural segment and a bearing structural segment which are sequentially connected from top to bottom. The upper pile body is arranged outside the force transferring structural segment in a sleeving mode, the bottom of a reinforcement cage of the upper pile body matches the variable-section structural segment, and the separation formwork is arranged between the upper pile body and the force transferring structural segment. On the premise that the settling volume at the top of the pile meets the deformation requirement of an upper structure, the bearing performance of whole-pile-length side friction force and pile end resistance can be fully achieved, and therefore the overall bearing capacity of the friction pile is improved; under the same upper loads, the needed pile length or pile diameter is smaller, settlement deformation of the pile top can be effectively controlled, and then engineering cost is reduced.