Background: Fractures of the middle and distal diaphysis of the forearm are common in children. Conservative treatment is effective in this regard. Some studies have discussed the risk factors and predictive indicators of re-displacement; however, the objects of the study are all fixed with tubular plaster or double sugar splint. Objectives: This study was performed to determine the risk factors of re-displacement after closed reduction and double splint plaster fixation of unstable pediatric fractures of the middle and distal diaphysis of the forearm. Methods: This retrospective study was conducted on 57 patients undergoing closed reduction and plaster fixation after unstable diaphyseal fractures of the middle and distal forearm in Wuxi Children's Hospital of Nanjing Medical University within May 2014 to May 2020. A total of 35 male and 22 female subjects aged 6 - 9 years (average: 7.3 years) participated in this study. They were followed up for more than 6 weeks after fracture healing. According to whether experiencing a secondary displacement within 2 weeks after the fracture, the subjects were divided into two groups, namely displacement, and non-displacement. Gender, age, double fracture, reduction quality, and plaster fixation type were analyzed as relevant, effective factors. Results: All 57 patients were followed up, and all fractures reached clinical healing standards at the last follow-up. Moreover, 20 and 37 cases were in the shift and non-shift groups, respectively. No statistically significant difference was reported in gender (c2 = 0.168; P = 0.780), age (t = 1.003; P = 0.217), double fracture (c2 = 0.021; P = 1), and plaster fixation type (c2 = 0.416; P = 0.699) between the two groups. The reduction quality (c2 = 7.480; P = 0.025) showed a statistically significant difference. Binary logistic regression analysis showed that reduction quality was a risk factor for fracture relocation providing a predictive value. Conclusions: Good reduction quality can reduce the risk of fracture displacement.