Can I display authors in About Page from specific User Group?

Hi Zhenyu !
Currently, DW Simplex does not yet support to display authors in About Page from specific User Group. However, You can display the users that you want to display on the About page.
To do it, You can open the shortcodes.php file in the folder path “\wp-content\themes\dw-simplex\inc”. Find the line 27 to 30. Replace the following code:

     extract(shortcode_atts(array(
        "number" => '8'
    ), $atts));
    $authors = get_users('orderby=registered&oder=DESC&number='.$number);

With new code:

 extract(shortcode_atts(array(
  "number" => '8',
  "ids" => ''
 ), $atts));

 $authors = get_users('orderby=registered&oder=DESC&number='.$number.'&include='.$ids);

Then log in to Dashboard > Pages > Open About page, add the following shortcode:[authors ids=’1,2,3′] Notice: ‘1,2,3‘ is ID of the users that you want to display.
To Find the ID of user, please move through Users. Hover on user name, You can see the ID in the bottom your site. See the screenshot:
Hope this helps !