This study reports three rare cases of primary leiomyosarcoma (LMS) originating in the gastrointestinal tract. Among the three patients, one was male and two were females, aged 58 to 68 years. The tumors originated in the stomach in two cases and in the small intestine in one case. Histopathological examination of the surgical specimens showed that the tumors exhibited infiltrative growth, all invading the muscularis propria, and mucosal surface ulceration was observed in two cases. The tumor cells were spindle-shaped, arranged in bundles or interwoven patterns. The cytoplasm was abundant and eosinophilic, and the nuclei showed moderate to high atypia, with mitotic figures easily observed (50-100/50 HPF). Immunohistochemical staining revealed that the tumor cells were positive for SMA(3/3), Desmin and Caldesmon(2/3), but negative for CD117, Dog-1, and CD34(3/3). The Ki-67 proliferation index ranged from 30% to 80%. The follow-up periods of the three patients ranged from 11 to 53 months. Two patients were tumor-free, while one patient developed pancreatic metastasis 30 months after surgery but remained alive at the last follow-up at 53 months. LMS is a rare soft tissue sarcoma, and primary gastrointestinal LMS is extremely rare. The definitive diagnosis of the disease is based on postoperative pathological examination. LMS tumor cells are spindle-shaped, with eosinophilic cytoplasm and significant nuclear atypia, expressing smooth muscle cell markers. It is necessary to differentiate from gastrointestinal stromal tumors and other spindle cell tumors. Surgical resection remains the primary treatment, but the prognosis is generally poor, highlighting the importance of accurate diagnosis.