Gastrointestinal stromal tumor (GIST) were previously known as smooth muscle tumor like leiomyoma or leiomyosarcoma. Most of them were histologically spindle cell tumors, usually of mesenchymal origin. Stromal tumors account for about 1% to 2% of gastric malignant tumor, and the most important characteristics is their indolent, slow-growing nature, rendering most common definitions of malignancy invalid and inapplicable. The tumors are generally found deep within the stroma and submucosa, and only about half have an intragastric component, detectable by radiography, endoscopy or endoscopic ultra-sonography (EUS). Especially EUS is a valuable technique for diagnosing GIST. We experienced a 35-year-old female patient who complained right upper quadrant pain. She was diagnosed as subserosal stromal tumor by gastrofiberscopy, EUS, abdominal CT and operation. We report a case of gastric subserosal stromal tumor with a review of relevant literatures.