The influence on outcoupled phase mode by introducing intracavity tilt-perturbation in confocal unstable resonators is researched by adopting Fox-Li prony method. The distribution of wavefront has been analyzed by using Zernike aberration and mode reconstruction theory. The front 35-order Zernike aberration coefficient, point spread function (PSF) and the integrated relative far-field intensity are obtained, so the beam quality can be known fully. The properties of mode distortion are also studied experimentally by adopting Hartmann-Shack (H-S) wavefront sensor. Finally, a set of control system for intracavity perturbation is constructed and the correction for intracavity low-order aberration is performed experimentally. The result of intracavity correction shows that the system can achieve good correction for static intracavity perturbation when the control loop is closed after tilt is introduced. The front 10-order Zernike aberration, the peak value (PV) and root-mean-square (RMS) error of the wavefront have been reduced remarkably.