Beam-converting annular resonator (BCAR) possesses outstanding characteristics of high extraction efficiency and near-diffractive beam quality. It is applied specially to annular HF/DF gain medium. In this paper, numerical model of rear cone misalignment and compact leg tilt is presented, and this numerical model has been used in physical optics code. The numerical result shows that the output power is insensitive to rear cone decentration and compact leg tilt, but beam quality is very sensitive to the decentration and tilt. The rear cone decentration and compact leg tilt can both result in a phase shear and twist on the optical field, and lead to phase jump and tilt along the misalignment direction. When the misalignments increase, the phase distribution of BCAR output field is twisted more severely. The directions of misalignments have little effects on the output field. Among these misalignments, rear cone decentration has more severe effect on the output field, and it must be controlled carefully in engineer.