In this paper, it has been experimentally verified that the planop lano resonatorwith internal lens behaves steadier than plano concave resonator in an Cr4 + ∶Nd3 + ∶YAG self2Q2switch laser. And also, some especial phenomenon, such as the extremum p roperties of both the output power and repetitionrate alongwith pumping power increasing, is observed. By theoretical analysis, the major reason of extremum properties is exp lained by the dynamical variation of both the pump ing rate and the radius of foundational2mode laser beam, which are excited by thermal lens effectin laser crystal. Furthermore, by adjusting resonator length, focuslength and location of internal lens, the output characters of laserwould be changed, which means that the planop lano resonator rep resents more designflexibility than plano concave resonator in self2Q2switch laser.