The invention discloses a clamp for an aero-engine nozzle angle test and a clamping method of the clamp, and is to carry out angle test conveniently before nozzle installation for an inclined-type bent nozzle having no horizon reference. The adopted technical scheme is characterized in that the clamp comprises a support arranged on the top portion of an angle flow tester spray box; and the support is in an angle structure provided with an installation inclined plane and a bottom plane, wherein the installation inclined plane and the bottom plane form an included angle; the installation inclined plane is provided with a U-shaped groove convenient for a nozzle to pass through; and the installation inclined plane is further provided with location holes and screw holes for installing screw rods. The location holes are used for installing cylindrical protrusions on the outer plane of the nozzle. The bottom plane of the support is provided with an installation hole for installing a cylindrical spray head of the nozzle. The installation inclined plane of the support is provided with pressure plates, wherein the pressure plates are respectively a cover-pressing-type pressure plate, and each pressure plate is provided with key groove facilitating to adjust the position of the pressure plate. The screw rods pass through the key grooves and enable the pressure plates to be installed to the support; and the pressure plates are matched with the support, and thus the nozzle is fixed.