How to remove the horizontal line of the header with back watermark in WORD?

Click View-Header and Footer, select the small arrow on the header (remember to select it), then Format-Border and Shading, change the setting to None in the border option, and then confirm.

Click View-Header and Footer, then position the cursor in the header and click the border option under Format-Border and Shading. At this time, the application scope shows "text", just change it to "paragraph". ?

First open the document, click format style, select all styles under the list, then select the header in the style, click change, select the format in the change dialog box, and click the format to select the border. Formatting and borders will appear. ?

Then add "header and footer" (view → header and footer), and you can see that the horizontal line under the header has disappeared.