A new scheme which can generate special intensity distribution hollow laser beams-double half-Gaussian hollow beams by modified Cassegrain optical system is presented, and the optical system is composed of reflecting positive conic mirror and spheric reflector. The factors such as conic angle of positive conic mirror, the divergence angle of Gaussian beams and the ature radius of spherical reflector, which influence on the ratio of ring width to radius and spherical aberration, are analyzed in detail. By adjusting the above parameters, the double half-Gaussian hollow beams with the ratio of ring width to radius being 0.1～1 can be easily obtained. And the experimental results show that the hollow beams which are generated by the modified Cassegrain optical system is double half-Gaussian hollow beams. The research provides the theory of generating the double half-Gaussian hollow beams with the ratio of ring width to radius being 0.1～1 and establishes solid foundation in the fields of scanning image and communication.