List subIndex = new List();string A = "ssddxx等级:12kkkcxc12kkk等级:31sxsd1xd等级:52kkkcsdfsdf2k等级:44";int ii = A.IndexOf("等级");while (ii >= 0 && ii < A.Length){subIndex.Add(ii);ii = A.IndexOf("等级", ii + 1);}int[] arrIndex = subIndex.ToArray(); //你要的数组