Background: The age at which to initiate operation in auricular reconstruction is still controversial.The growth of rib cartilages closely related to age determines the feasibility and results in auricular reconstruction.The aim of this study is to explore a predictable method of guiding when to begin surgery for younger children with microtia ranging in age from 5 to 10 years.Methods: Rib cartilage and healthy ear cartilage framework were reconstructsed by MSCT with low dose to assess the ribs and guid surgery.The length of eighth rib cartilage combined with the length of helix of healthy ear cartilage framework from foot of helix to the junction of earlob were measured and analysised.The surgeon practiced the surgery when cartilages satisfied surgery need.The results were evaluated.Results: The measurement of rib 8 preoperation were significantly correlated with intraoperatively measured cartilage length (P<0.05),indicate the credibility of image measuring in clinical applications.From years 5 to 10 the growth of rib 8 is not linear but less consistent.Guided by the proximity of the length of rib8 and helix of healthy ear cartilage framework, satisfactory surgical results were achieved in 76 (62.8%) of total 121 cases with completely helix fabrication using rib8 and 18(14.9%) cases whose rib8 slightly shorter with helix fabrication by adjusting the length of helical crus in stent;acceptable surgical results were achieved in 17(14.0%) cases with helix fabrication by splicing;9 cases(7.4%) with insufficient length delayed operation;1 early case(0.8%) with insufficient length and no cartilage left, the result was not up to the mark due to our few experiences in early stage.Conclusions: Development of the eighth rib cartilage is variable, rib cartilage assessment refer healthy ear offered a predictable method guiding reconstruction timing to initialize personalized treatment of younger patients with microtia.