Background: Rotating Gantry is widely used in proton therapy due to its small radiation damage toward the normal tissue around the tumor.Proton therapy gantry optics which plays an important role in rotating gantry is under design in Shanghai Advanced Proton Therapy Facility(APTRON).Purpose: To generate a circular beam profile at iso-center while the gantry rotates with different angles.Methods: Different gantry optics matching techniques are used to calculate the beam optics.These methods include the round-beam method(RBM) or not in the front of vacuum window

and use RBM at iso-center.The simulations of beam profile at iso-center after the beam passing through nozzle and body tissue are carried out with Geant4 software.Results: The beam profile at iso-center can be taken as similar among three cases

and there is slight improvement using RBM.Conclusions: The designed proton therapy gantry optics is intensive to the rotation angle and is applicable for the real application.