Abstract: Objective To investigate the changes in serum levels of microRNA-922 (miR-922), 25-hydroxyvitamin D₃ (25-OH-D₃) and pre-B-cell leukemia homeobox 3 (PBX3) in children with acute myeloid leukemia (AML) and their clinical value in evaluating prognosis. Methods Seventy-three children with AML were enrolled in AML group, and 87 healthy children who underwent routine physical examinations during the same period were included in control group. The AML patients were further divided into poor prognosis (n=21) and good prognosis (n=52) groups based on their outcomes. Serum levels of 25-OH-D₃, miR-922 and PBX3 were compared among the groups. Multivariate Logistic regression analysis was used to identify factors associated with poor prognosis in AML patients. Receiver operating characteristic (ROC) curves were constructed to evaluate the prognostic value of serum 25-OH-D₃, miR-922, and PBX3 levels in AML patients. Results The serum levels of 25-OH-D₃ in the AML group were significantly lower, and the levels of miR-922 and PBX3 were significantly higher than those in the control group (P<0.05). The stratified ratio of medium-high risk, white blood cell count, proportion of abnormal chromosome karyotype, serum miR-922 and PBX3 levels in the poor prognosis group were significantly higher, and the serum 25-OH-D₃ level was significantly lower than that in the good prognosis group (P<0.05). Factors associated with poor prognosis in AML patients included middle-and high-risk stratification, high white blood cell count, abnormal karyotype, low 25-OH-D₃ level, high miR-922 level, and high PBX3 level (P<0.05). The areas under the curves (AUC) for predicting poor prognosis in AML patients using serum 25-OH-D₃, miR-922 and PBX3 were 0.815, 0.827 and 0.853, respectively. PBX3 had the highest predictive value, followed by miR-922 and 25-OH-D₃. Conclusion The serum levels of 25-OH-D₃ are decreased in children with AML, while the levels of miR-922 and PBX3 are increased.Serum levels of 25-OH-D₃, miR-922 and PBX3 have high prognostic value in children with AML.