Background: Studies reported that soluble B7-H4 (sB7-H4) was significantly related to the progression and prognosis of inflammatory diseases, and whether sB7-H4 is related to the severity and prognosis of acute pancreatitis (AP) timely has not been reported. Materials and methods: Clinical database data of 446 AP patients were retrospectively collected, and the correlation between the expression serum levels of sB7-H4 with inflammatory factors and prognostic scores was analysed in AP patients. Results: Soluble B7-H4 was significantly correlated with IL-6, IL-8, TNF-α, PCT, CRP levels and WBC count (P < .01), with correlation coefficients of R = .61, .53, .46, .60, .57 and .47, respectively, and AUCs were 0.905, 0.837, 0.797, 0.858, 0.890, 0.841 and 0.855, respectively. In addition, sB7-H4 was significantly correlated with the Ranson score, APACHE II score and BISAP score (P < .001), with correlation coefficients of R = .58, .63 and .59, respectively. The AUCs of assessing local complications of AP were 0.908, 0.863, 0.785 and 0.844, respectively; assessing organ failure were 0.872, 0.790, 0.796 and 0.857, respectively; and assessing in-hospital mortality were 0.839, 0.821, 0.796 and 0.823, respectively. Conclusions: Soluble B7-H4 could be used as a marker for the diagnosis, severity assessment and poor prognosis assessment of AP patients, which may have potential clinical applications.