1. In the excel table, list two columns of data, compare the data in column B and column A, filter out which data in column B are different, and mark them in red.

2. Select column B first. Click the left mouse button directly on column B to select it. Start-> Conditional Format-> New Rule:

3. Select the last item "Use formula to determine cells to format" in "Select rule type":

4. In the box marked in red, enter the formula: =countif(a:a, B 1)=0 (meaning of the formula: compare all the data in column A with the data in column B1). If there are duplicate values, add 1, it will appear n times, and the value of the formula is n ... If it does not appear, the result is 0).

5. In the red box, click "Format": mark the different filtered data.

6. In this example, the color of "font" is used as the mark of "different data". Choose the font color according to your personal preference. In this case, choose red. Click OK.

7. Return to this interface and click OK.

8. Rendering: The red data in column B is the data that does not exist in column A..