The invention belongs to the technical field of novel agriculture, and particularly relates to an automatic vegetable harvesting device based on aquaponics and a using method thereof. The automatic vegetable harvesting device comprises a fish box, a fixing block is fixedly connected to the fish box, a planting plate is rotatably connected to the fixing block, and three rectangular cavities are formed in the side wall of the side, away from the fixing block, of the fish box; and threaded sleeves matched with the rectangular cavities are rotatably connected to the fish box, and a first screw rodis in threaded connection with the interior of the threaded sleeve located in the middle. According to the automatic vegetable harvesting device, water spinach can be harvested in time under the cooperation of an air cylinder and a transmission mechanism by utilizing the growth height change of the water spinach, the harvested water spinach can be automatically conveyed to a water spinach storingbox to be stored, meanwhile, water can be supplemented to roots of the water spinach in time, and the water spinach roots are promoted to grow again; and in the whole process, the integrated processof cutting, collecting, clearing and re-cultivating can be realized, so that the manpower is greatly saved, and the treatment efficiency of vegetables is improved.