To investigate and analyze the changes of serum inflammatory factors in patients with delayed fracture healing in platelet-rich plasma therapy.Methods 98 fracture patients admitted to our hospital from April 2020 to April 2021 were selected and treated with platelet-rich plasma combined with steel plate internal fixation. According to whether delayed fracture union occurred within 6 months after operation, they were divided into delayed union group of 37 cases and 61 cases in the normal healing group. Serum samples were collected from patients at 1 week, 4 weeks, 8 weeks, and 12 weeks after fracture, and enzyme-linked immunosorbent assay was used to detect serum human soluble intercellular adhesion molecule-1 (sICAM-1), human the levels of inflammatory factors such as soluble vascular cell adhesion molecule-1 (sVCAM-1), tumor necrosis factor-α (TNF-α), and the ROC curve was drawn according to their levels to evaluate its predictive value for predicting delayed fracture union. Serum bone gla protein (BGP), procollagen type Ⅰ N-terminal propeptide (PINP), alkaline phosphatase (ALP), the levels of bone biochemical metabolism indexes such as insulin like growth factor-1 (IGF-1), and the relationship between bone biochemical metabolism indexes and inflammatory factors were analyzed by Pearosn. Results At 1 week after fracture, there was no difference in serum sICAM-1,sVCAM-1, TNF-α and other inflammatory factor levels between the delayed union group and the normal union group (P＞0.05). The levels of serum sICAM-1, sVCAM-1, TNF-α and other inflammatory factors in the healing group were higher than those in the normal healing group (P＜0.05). TNF-α level first increased and then decreased, but the fluctuation of inflammatory factor levels in the delayed healing group was more obvious than that in the normal healing group (P＜0.05). At 1 week after fracture, there was no difference in serum BGP, PINP, ALP, IGF-1 and other bone biochemical metabolism indexes between the delayed healing group and the normal healing group, and there was no difference in serum ALP levels between the two groups at each time point (P＞0.05). At 4 weeks, 8 weeks, and 12 weeks of fracture, the serum BGP level in the delayed union group gradually increased and was higher than that in the normal union group, and the serum IGF-1 level gradually increased but was lower than that in the normal union group. The level of serum PINP in the healing group was lower than that in the normal healing group (P＜0.05). The results of Pearson correlation analysis showed that the levels of serum sICAM-1, sVCAM-1, TNF-α and other inflammatory factors were positively correlated with serum BGP (r=0.523, P=0.000), and negatively correlated with serum IGF-1 (r=0.000).-0.467,P=0.000). The results of ROC curve analysis showed that the area under the curve of serum inflammatory factor levels for the diagnosis of delayed fracture union was higher than 0.7 at 8 weeks after fracture, indicating that it has a good diagnostic value, and the combined detection has higher sensitivity for the diagnosis of delayed fracture union(P＜0.05).Conclusion The levels of serum sICAM-1, sVCAM-1, TNF-α and other inflammatory factors in patients with delayed union increased first and then decreased with the increase of fracture time. The delayed union of fractures has certain reference significance