Private Sub Command1_Click()
Dim Rs As New ADODB.Recordset
Dim Conn As New ADODB.Connection
Dim Ssql As String
Conn.Open "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;pwd=sa;Initial Catalog=vb;Data Source=LPLBOKE"
Ssql = "select * from xscj where id='" & Text3.Text & "'"
 If Rs.EOF = False Then(运行到此行时提示，对象关闭时，不允许进行操作！)
   MsgBox "学生编码重复，请修改编码！"
   Else
   Ssql = "insert into xscj (name,stroe,id) values ('" & Trim(Text1.Text) & "','" & Trim(Text2.Text) & "','" & Text3.Text & "')"
   Rs.Open Ssql, Conn
   MsgBox "添加成功！"
   Text1.Text = ""
   Text2.Text = ""
   Text3.Text = ""
 End If
End Sub

rs.open要放在rs.eof的前面、。
数据集都没打开，你只连接了数据库，但还没进行查询啊

Private Sub Command1_Click()
Dim Rs As New ADODB.Recordset
Dim Conn As New ADODB.Connection
Dim Ssql As String
Conn.Open "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;pwd=sa;Initial Catalog=vb;Data Source=LPLBOKE"
Ssql = "select * from xscj where id='" & Text3.Text & "'order by id"
 
Rs.Open Ssql, Conn
      If Rs.EOF = False Then
        MsgBox "学生编码重复，请修改编码！"
    Else
        Ssql = "insert into xscj (name,stroe,id) values ('" & Trim(Text1.Text) & "','" & Trim(Text2.Text) & "','" & Text3.Text & "')"
      Rs.Open Ssql, Conn（加了后这一句提示，数据打开，不允许操作！！)
        MsgBox "添加成功！"
        Text1.Text = ""
        Text2.Text = ""
        Text3.Text = ""
        
 End If

请帮忙改一下。数据库表，XSCJ，字段ID NAME(姓名)　stroe（成绩）

Ssql = "insert into xscj (name,stroe,id) values ('" & Trim(Text1.Text) & "','" & Trim(Text2.Text) & "','" & Text3.Text & "')"
此句后，如果不加   Rs.Open Ssql, Conn
执行成功，但数据库中没有插入数据

Ssql = "select * from xscj where id='" & Text3.Text & "'order by id"
Rs.Open Ssql, Conn
    If Rs.EOF = False Then
        MsgBox "学生编码重复，请修改编码！"
        
    else
    rs.addnew      
        MsgBox "添加成功！"
        rs(0)=Text1.Text
        rs(1)=Text2.Text
        rs(2)=Text3.Text
        Text1.Text = ""
        Text2.Text = ""
        Text3.Text = ""
        rs.update
End If
   rs.close

rs.addnew      
        MsgBox "添加成功！"
        rs(0)=Text1.Text
        rs(1)=Text2.Text
        rs(2)=Text3.Text
        Text1.Text = ""
        Text2.Text = ""
        Text3.Text = ""
        rs.update
如果此段代码用SQL语句写，怎样写，刚才我自己试了一种方式可以运行，但比较烦锁，如下（红字）
Private Sub Command1_Click()
Dim Rs As New ADODB.Recordset
Dim Conn As New ADODB.Connection
Dim Ssql As String
Conn.Open "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;pwd=sa;Initial Catalog=vb;Data Source=LPLBOKE"
Ssql = "select * from xscj where id='" & Text3.Text & "'order by id"
 Rs.Open Ssql, Conn
    If Not Rs.EOF Then
            MsgBox "学生编码重复，请修改编码！"
            Rs.Close
            Text3.SetFocus
            Exit Sub
    End If
If Conn.State <> adStateClosed Then
   Conn.Close
End If
Conn.Open "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;pwd=sa;Initial Catalog=vb;Data Source=LPLBOKE"
   If Text1.Text <> "" Then
       Ssql = "insert into xscj (name,stroe,id) values ('" & Trim(Text1.Text) & "','" & Trim(Text2.Text) & "','" & Text3.Text & "')"
       Rs.Open Ssql, Conn
      MsgBox "添加成功！"
      Text1.Text = ""
      Text2.Text = ""
      Text3.Text = ""
   End If

End Sub

还有就是你那个语句，我复制后运行到rs.addnew   ，提示   
当前记录集不支持更新，这可能是提供程序的限制，也可能是选定锁定类型的限制

Ssql = "insert into xscj (name,stroe,id) values ('" & Trim(Text1.Text) & "','" & Trim(Text2.Text) & "','" & Text3.Text & "')"
的格式是对的。id如果是数字的话，就不要‘’了。
在
If Text1.Text <> "" Then
       Ssql = "insert into xscj (name,stroe,id) values ('" & Trim(Text1.Text) & "','" & Trim(Text2.Text) & "','" & Text3.Text & "')"
conn.execute sql
MsgBox "添加成功！"
      Text1.Text = ""
      Text2.Text = ""
      Text3.Text = ""
   End If

前面打开的数据集rs，要记得关掉。rs.close

当前记录集不支持更新，就代表你已经打开记录集了，应该是锁定类型有关。 可能默认是只读的。adLockReadOnly

我一般都设为adLockOptimistic,