【Objective】To observe the effect of reaming acetabular in two different depth on the outcome of total hip arthroplasty（THA）.【Methods】119 consecutive patients with femoral neck fracture scheduled for THA were divided ran? domly into 2 groups（group A and B）. For the patients in group A，we ream the fossa acetabuli until the subchondral bone in the superior wall revealed；for the patients in group B，we ream the fossa acetabuli until the subchondral bone in the anterior and posterior wall revealed，which means part of the subchondral bone in the anterior and posterior wall retained. Duration of surgery，amount of bleeding during surgery，the stability of the acetabular prothesis after first implantation， Harris hip score were recorded and analyzed.【Results】The operations for patients in group A take more longer time， with more amount of bleeding during operation contrast to group B（P＜0.05）. It’s more difficult to obtain satisfied initial stability for the acetabular prosthesis in group A than in group B（P＜0.05）. The patients’HHS in group A are lower than that in group B 3 months after the operation（P＜0.05）whereas no statistical difference is found 2 years after the op? eration（P＞0.05）.【Conclusion】Retaining subchondral bone in the anterior and posterior acetabular wall is timesaving in THA，with less amount of bleeding and more easier to obtain initial stability during the operation，could achieve more satisfied function in short-term follow up.