Gastrointestinal stromal tumors (GISTs) are the most common submucosal tumors (SMTs) of the stomach. The 2022 European Society of Oncology ESMO Diagnosis and Treatment Guidelines recommend that GISTs undergo biopsy with a clear pathological diagnosis and should be removed unless there are significant complications. But currently, the diagnostic rate of EUS-FNA for upper gastrointestinal subcutaneous lesions is less than 60%. In recent years, mucosal cutting biopsy (MCB) has become an effective method for diagnosing SMTs. Regardless of whether the SMTs are large or small, the application of MCB technology can quickly obtain pathological tissue under direct visualization, and its immunohistochemical pathological diagnosis rate is relatively satisfactory. MCB technology has great potential in the biopsy of SMTs, but there is currently no comparison of results between two technologies in randomized controlled trials. The purpose of this study is to design a randomized controlled trial to compare the diagnostic rates of EUS-FNA and MCB techniques for tissue pathology (including immunohistochemistry) of SMTs, in order to improve the diagnostic accuracy of SMTs in our hospital and improve patient prognosis.