Abstract: Objective To study the clinical effect of calcium sulfate–based bone graft injection and core decompression on early-stage femoral head necrosis. Methods From March 2005 to January 2009,28 patients（24 males and 4 females） with early-stage femoral head necrosis at an average age of 35.7（21-57） years were treated with calcium sulfate–based bone graft injection and core decompression by off-center drill.A 2.5mm K-wire was inserted from the proximal lateral femoral cortex into the center of femoral head necrosis under the guidance of G-arm imaging.Then a core reamer and an off-center drill were inserted in the guide pin.The necrotic bone and its margins were completely removed under an arthroscope.Calcium sulfate–based bone graft injection was injected into the bone channel and cavity. Results Twenty-four patients were followed up for an average period of 38 months（12-52 months）.The outcome was evaluated by Harris score.The mean preoperative Harris hip score was 62.5（52-74）,and increased to 84.5（63-93） after operation.According to the Harris hip score,the results were excellent or good in 18 patients（75%）,fair in 5 patients（20.8%）,and poor in 1 patient（4.2%）,respectively. Conclusion Calcium sulfate–based bone graft injection after core decompression with off-center drill plays a supportive role in preventing collapse of femoral head with satisfactory results.