The invention provides a small portable self-adaptive hydraulic pipe bender. The pipe bender comprises a forming die, a compression bar, a pressing bar, a connection bar, a piston, a pipe clamp, a pressing block, a forming die hinge pin, a pressing bar hinge pin, a pressing block hinge pin, a manual hydraulic pump and a high-pressure hose. The forming die is a body structure, and the ends of the pipe clamp and the pressing bar are hinged to the forming die through the forming die hinge pin. The middle of the pressing bar is hinged to the pressing bar hinge pin through the connection bar, the pressing block is hinged to the other end of the pressing bar through the pressing block hinge pin, the piston is disposed in an oil cylinder in the forming die, and the manual hydraulic pump is used for providing oil pressure. During operation, a straight pipe to be bent is attached to the forming die through the pipe clamp and the pressing block, the manual hydraulic pump is pressed repeatedly to generate high-pressure oil to push the piston to move, the connection bar is pushed by the piston and pulls the pressing bar to rotate, and the pressing bar pushes the pressing block to impose bending moment on the pipe to bend the pipe. The pipe bender has the advantages of being portable, compact in structure, large in bending moment, self-adaptive to changes, applicable to pipe bundle bending within limited operation space and capable of preventing producing of defects of pits, indentations and the like on the surfaces of pipes.