Changes in human body parameters influence on the geometry of the ribcage in children, directly affecting the form of chest injury. A limited number of existing children's ribcage geometric models were developed using the parameters of specific body characteristics. CT 3D reconstruction，semi-automatic point selection，ribcage posture adjustment, statistical analysis，and Radial Basis Function（RBF） neural network deformation were applied to 61 CTs，and then a parametric geometric model for children's ribcage aged 3~12 years in China based on the age, height，Body Mass Index（BMI）， and gender was developed. Using the proposed parametric geometric model，the children's ribcage geometry models depending on the age（3~12 years old），height，BMI，and gender can be quickly obtained. The average geometric accuracy of the predicted ribcage geometry model for children aged 3~12 years was 5.2 mm, and the average geometric accuracy of the first to the twelfth pairs of ribs was at most 7.0 mm, and at least 4.5 mm. The parametric geometry model can be used to study the effect of human body parameters on the geometry of children's ribcage and its impact on children's chest injury.