The effects of intra- cavity aberration compensation based on negation of phase or calculation of geometrical optics in positive-branch confocal unstable resonator is not ideal because of the different sizes of oscillation laser (plane wave and spherical wave) on optical elements and light deflection caused by the aberration.A non-conjugated intra-cavity aberration compensation method based on the relaxation iterative approximation algorithm using a collimated probe beam wavefront as the reference is presented. In experiment,the effects of compensation referenced single pass probe and round-trip probe are compared. It can be found that the beam quality of output guided light cannot be improved in the compensation using single pass probe. The round-trip probe wavefront can begin to stabilize and the root mean square (RMS) of residual error is less than 0.1 mm after 7~9 iterative steps, when the value of RMS of the random intra-cavity aberration is 0.3~0.4 mm. The β value of output guided light, which is as the evaluation criterion, can be decreased from 11.2 to 2.6 with the compensation. By analyzing of the relationship and difference between the guided light and the oscillation laser, it can be inferred that the beam quality of output laser in an active unstable resonator will be improved using this aberration compensation method.