Objective To analyze the natural development of the residual subluxation after early close reduction for developmental dislocation of the hip,and to seek the early surgical timing and indication.Methods The research included 36 patients (48 hips) born before January 2000 who showed residual subluxation after close reduction in one year.All of patients had serial X-ray radiographs at every follow-up point.The radiographs were assessed using acetabular index (AI),Reimers index,center edge (CE) angle and the orientation of the sourcil of the acetabulum.The last follow-up results were evaluated according to the Severin classification,and Severin grade Ⅰ and Ⅱ were defined as satisfactory group and Severin grade Ⅲ and Ⅳ as unsatisfactory group.Then we compared and analyzed the serial radiological parameters between satisfactory and unsatisfactory groups.Results The mean age at close reduction was 1.6 years.At the last follow-up,the mean age was 13.8 years.The satisfactory group comprised 18 hips (37％),whereas the unsatisfactory group comprised 30 hips (63％).At the age of three to four years,there was a significant difference between the two groups in the Reimers index (34.4％±4.5％ vs.43.0％±4.6％,P ＜ 0.05).And at four to five years old,there were significant differences for both Reimers index and CE angle (29.3％ ±7.2％ vs.40.0％±6.2％,P ＜ 0.05; 21.0°±5.5° vs.10.6°±5.2°,P ＜ 0.05).When the Reimers index ＞38％ at the age of three to four years,18 of 18 hips fell into the unsatisfactory group.And when Reimers index ＞33％ at the age of four to five years,26 of 30 hips had unsatisfactory result,and in addition to that the sourcil orientation was upward,26 of 26 hips fell into the unsatisfactory group.Conclusion To avoid early osteoarthritis,surgical correction for residual subluxation was recommended if the Reimers index ＞38％ at the age of three to four years or the Reimers index ＞33％ with the sourcil upward at the age of four to five years.