Crohn's disease (CD) is a chronic nonspecific inflammatory disease of the intestinal tract whose etiology is not yet fully understood, and can present with serious complications such as intestinal obstruction, perforation, abdominal abscesses, and fistulae. Currently, the main therapeutic drugs for CD include aminosalicylic acid preparations, glucocorticoids, immunosuppressants, and biological agents. With the development of medical technology, small molecule preparations have begun to be applied to moderate-to-severe Crohn's disease. Upadacitinib is a novel oral small molecule agent that is a highly selective JAK-1 inhibitor. A large real-world study showed that in refractory moderate-to-severe CD, upadacitinib showed a clinical response rate of 76.5% and a clinical remission rate of 70.6% at 8 weeks of treatment. Intestinal ultrasound (IUS) is a noninvasive, reproducible, convenient, and inexpensive test that can greatly increase the frequency of assessing treatment response and speed up the clinical decision-making process.The 2019 ECCO-ESGAR guidelines recommend intestinal ultrasound for disease monitoring in patients with CD. There are no validated indicators to predict the efficacy of upatinib treatment in patients with moderate-to-severe CD in the currently available studies. Currently, there are no national or international studies in which intestinal ultrasound predicts the efficacy of upatinib therapy. Therefore, we propose for the first time that intestinal ultrasound be used as a method to predict the response to upadacitinib in CD patients, with the aim of providing evidence to guide the development of individualized treatment plans.