The adaptive optics system with Rayleigh guide star could compensate the image in observational astronomy, and could improve sky coverage. Projecting a suitable Rayleigh guide star is the precondition of adaptive optics with laser guide star. To realize the image compensation in observational astronomy, a laser launched system was designed. All kinds of parameter were analyzed and a suitable method of launching a laser guide star was completed. First, based on the demand of adaptive optics system with Rayleigh guide star, all kinds of parameter of laser box were probed. Next, the laser launched telescope aperture and the guide star spot size were analyzed according to the turbulence theory. Then, the laser launched system was designed by Zemax. The aperture of launching telescope is 260 mm. The optimal altitude of laser beam waist is 9.8 km, with Rayleigh guide star at 10-11 km. The laser spot size is 0.45″ without turbulence and less than 1″ with turbulence. Finally, the system was analyzed with tolerance by Zemax, and the results demonstrated that the system was easily to process. The laser projected system could suffice the demand of laser guide star adaptive optics and the method to design the system could be widely used.