It is difficult to ensure perfect alignment of the laser resonator in the process of actural assembly and operation process. Therefore, it is necessary to study the stability of resonator. The "Rigord analysis method" is used to analyze the variation of power extraction efficiency for parabolic mirror off-axis unstable resonator and spherical mirror resonator, when the angle is out of adjustment. The output characteristics of the two types of resonator are discussed, and the stability of the off-axis unstable resonator is studied when the radius of curvature of the resonator mirror increased. The results show that the power extraction efficiency of the parabolic mirror resonator is 5.6% higher than that of the spherical mirror one when mirror tilt angles varied between ―6 mrad to 6 mrad. For parabolic mirror resonator, the power extraction efficiency is 3.5% higher that of the spherical mirror resonator, when the variation of cavity length is in the range of ―1 mm to 1 mm. When the radius of curvature of resonator mirror is increased by 2 mm, the power extraction efficiency of the parabolic mirror resonator is increased and the anti-misalignment characteristics are better.