The invention relates to a device for an explosive fracturing simulation experiment of a horizontal well and an application of the device. The device comprises a rock sample clamping device, an impact loading device and a control analysis device, wherein the rock sample clamping device comprises a cylinder body; rock cores of different characteristics can be put into the cylinder body; a hole inner pressure inlet, a confining pressure inlet, a confining pressure relief opening, an air outlet and a seepage channel outlet; the impact loading device comprises an ultrasonic generator, a transducer, an amplitude-change pole and an impact hammer; the impact hammer is controlled to impact a movable plunger at one end of the cylinder body through a computer and the ultrasonic generator; and impact force is loaded to the rock cores in the cylinder body, confining pressure is loaded through the confining pressure inlet and inner pressure is loaded through the hole inner pressure inlet. The device can be used for exploring damage responses of explosion impact in a horizontal wellbore to the rock cores of different lithologic characters and lengths, meanwhile, accurate experiment control operation can be achieved, effective data analysis and statistics can be carried out, so that the experiment effect is good and the action is obvious.