Gecacitinib hydrochloride is a novel JAK/ACVR1 inhibitor approved for intermediate- and high-risk myelofibrosis (MF). Clinical and real-world data demonstrate significant efficacy in spleen reduction, symptom relief, and anemia improvement, with favorable safety and tolerability. Preclinical studies confirm that this agent can mitigate GVHD and suppress inflammation. MF patients undergoing allo-HSCT are at risk of delayed engraftment and aGVHD. Based on the immunomodulatory effects of JAK inhibitors, gecacitinib is expected to have potential for aGVHD prophylaxis. This study aims to evaluate the efficacy and safety of geltrectinib hydrochloride combined with ATG for preventing aGVHD in MF patients after allo-HSCT.