The invention provides a multifunctional pet body-building assisting cage which not only can be used for storing a pet, but also can be combined with a household treadmill and realizes the aim of pet body-building. The multifunctional pet body-building assisting cage comprises an upper frame and a movable base which can be separated from the upper frame, four universal wheels are all arranged at the bottoms of the upper frame and the movable base, wherein a base net for bearing the pet is arranged at the upper part of the movable base, and a bearing plate for storing excrements of the pet canbe inserted at the lower part of the movable base; a main door is arranged at the front side of the upper frame, and an assisting door is arranged at the left side of the upper frame and can be overturned upwards around hinges; and when the multifunctional pet body-building assisting cage is used, the assisting door is opened, and the upper frame is pushed away from the movable base onto the treadmill, therefore, the use is convenient. The invention can be also used as a common pet cage, realizes a plurality of purposes in one object, saves the household expenses and greatly saves resources.