The specific steps to underline the Word header are as follows:

1. First, we open the word document in the computer, and after adding the header, an underline will appear below the text.

2. Double-click the header to enter the editing status of the header and footer.

3. Hold the cursor on the header, enter the starting style, and select "Text", and the underline will be deleted.

4. You can also select the text in the header.

5. Enter the start option, click the paragraph option, and select the "no border" option in "Border".

6. After clicking, the underline in the title will be deleted. The format of the header here has not changed either.