代码如下
void CADO::InitADO()
{
    ::CoInitialize(NULL);
    try
    {
        if (FAILED(m_pConnection.CreateInstance(__uuidof(Connection))))
        {
            AfxMessageBox("Create Instance failed!");
            return;
        }
        
    }
    catch(_com_error e)
    {
        AfxMessageBox(e.Description());
    }
   
    //Sleep(4000);
}

调用函数：
    UpdateData();
    m_ado.InitADO();
    CString strConnect;
    strConnect.Format("Provider=SQLOLEDB.1;Persist Security Info=TRUE;UID=sa;PWD=jiaojinge;Initial Catalog=Mydbse");//
   
   
    if (FAILED(m_pConnection->Open((_bstr_t)strConnect,"","",adModeUnknown)))
    {
        AfxMessageBox("Can not open Database!");
        m_pConnection.Release();
    }
   
    int id;
    CString password;
    CString strsql;

    strsql="select Password from Stu_base_info where name=m_User";
    _bstr_t bstrsql=strsql.AllocSysString();

    if(FAILED(m_ado.m_pRecordset->Open(bstrsql,_variant_t((IDispatch*)m_pConnection),\           //出错
        adOpenDynamic,adLockOptimistic,adCmdText)))
    {
        AfxMessageBox("Open table failed!");
        m_ado.m_pRecordset.Release();
    }

/*    _variant_t RecordsAffected;
    m_ado.m_pRecordset=m_pConnection->Execute("select Password from Stu_base_info where name=m_User",&RecordsAffected,adCmdText);
    */

错误提示：

是不是缺少了下面的语句
m_pRecordset.CreateInstance(__uuidof(Recordset));

1 如2楼所说: m_pRecordset.CreateInstance(__uuidof(Recordset));
2 strsql="select Password from Stu_base_info where name='m_User'";
3 BSTR bstrsql = strsql.AllocSysString();
if(FAILED(m_ado.m_pRecordset->Open(bstrsql,(IDispatch*)m_pConnection,adOpenDynamic,adLockOptimistic,adCmdText)))

谢谢楼上两位，哎，我把这些操作都写进了GetRecordset函数中，却忘了掉用这个函数，而是直接用_RecordsetPtr的open（）函数，悲剧。哎发现数据库操作太多的小细节需要注意