Endoscopic submucosal dissection (ESD) is a technique that allows curative treatment of early gastrointestinal neoplasia with organ preservation. However, it is a technically demanding procedure. Tissue traction plays a vital role in facilitating the visualization of the cutting line and the submucosal vessels, which usually only relies on the hood attached to the tip of the endoscope. However, when dealing with flat or large lesions, the absence of reliable traction in ESD contributes to its technical complexity and prolongs procedure duration. Various traction devices and techniques have been developed to provide tension for the dissection plane and optimal visibility during ESD. Most of these only provide static traction from a fixed angle, thus the effect of traction diminishes when the dissection continues. In contrast to the aforementioned traction methods, magnetic traction offers the ability to externally manipulate an internal magnetic retractor, simplifying the internal workspace. The proposed magnetic retractor is composed of a detachable clip from an hemoclip is affixed to a magnetic element. By adjusting the position of the external magnetic source, the magnetic retractor automatically couples and aligns with it, enabling simultaneous dynamic directional control during the ongoing ESD operation. A novel robotic magnetic countertraction system was developed (MAG-ESD). The system consists of two sections: an external permanent magnetic source and the disposable magnetic retractor. The external permanent magnetic source is composed by a large external permanent magnet (EPM) which held by robot arm to externally control the locomotion of the magnetic retractor within patient. The disposable magnetic retractor is a consumable surgical instrument that modified from a commercial hemoclip, which has small magnets hangs on the clip legs. The design of the disposable magnetic retractor eliminates the need for endoscope withdrawal which can be inserted through the instrument channel from the handle during ESD operations, like other common instruments. In the current pilot study, the novel MAG-ESD counetrtraction system would be tested in 20 patients who undergo gastric and colonic ESD, with the aim of evaluating the system efficacy and safety.