The present disclosure is related to systems and methods for isocenter calibration. The method includes providing a phantom including a first member and a second member with a fixed position relationship. The method includes acquiring, using a first device, at least one first image of the first member of the phantom. The method includes determining, based on the at least one first image, a first position relationship between a first isocenter of the first device and the first member. The method includes acquiring, using a second device, at least one second image of the second member of the phantom. The method includes determining, based on the at least one second image and the fixed position relationship, a second position relationship between a second isocenter of the second device and the first member. The method includes determining, based on the first position relationship and the second position relationship, a third position relationship between the first isocenter and the second isocenter.