The invention discloses a using method of a folding tent. The using method comprises the following steps: (1) in a transportation process, immersing a water cushion into water, putting the belt body above a car body, putting a black upper layer of the belt body at the top of a car, and tying the belt body to the top of the car, wherein water enters the belt body after running through activated carbon and a check valve; (2) after the car arrives at a camping site, taking down the tent and the water cushion from the car, then laying the water cushion on the ground and inserting a portal frame into the water cushion, then connecting an air inlet pipe of the tent with an air blower and starting the air blower, wherein tent cloth can be arranged on the portal frame after the portal frame and supporting posts are inflated; and (3) during a rest, putting the water cushion at the bottom of the tent, and then turning on an ultraviolet lamp tube, wherein people can sleep on the water cushion which is heated by sunlight radiation and has an appropriate temperature and light rays of the ultraviolet lamp tube run through a transparent part and can be transmitted to a place 10-15 meters away from the tent. By the using method, people can be protected from dampness when having a rest at night.