Note: Removing the primary key also removes the index that was created for the primary key.

Step 1: Open table from the database that you want to modify.

Note: Before you can remove a primary key, you must make sure that it doesn't participate in any table relationships. If you try to remove a primary key that is part of one or more relationships, Access warns you that you must delete the relationships first.

To delete a table relationship

If the tables that participate in the table relationship are open, close them. You cannot delete a table relationship between open tables.

1.    On the Database Tools tab, in the Relationships group, click Relationships.

2.    If the tables that participate in the table relationship are not visible, on the Design tab, in the Relationships group, click Show Table.

3.    Select the tables to add in the Show Table dialog box, and then click Add, and click Close.

4.    Click the table relationship line for the table relationship that you want to delete (the line becomes bold when it is selected), and then press the DELETE key.

5.   On the Design tab, in the Relationships group, click Close.

6.    After you delete the relationships, in the Navigation Pane, right click the table in which you want to remove the primary key and, on the shortcut menu, click Design View.

 Note: - If you don't see the Navigation Pane, press F11 to display it.

Step 2:- Click the row selector for the current primary key.

Note: - If the primary key consists of a single field, click the row selector for that field. If the primary key consists of multiple fields, click the row selector for any field in the primary key.

Step 3:- On the Design tab, in the Tools group, click Primary Key. The key indicator is removed from the field or fields that you previously specified as the primary key.