您可以在Wordpress上添加自定义仪表板徽标吗？

I want to replace the Wordpress logo in the dashboard on the top left? Where there's a 'W'

Is this possible?

Yes you can, 2 ways:

1. Plugin: White Label CMS wordpress plugin
2. Via code:

First you need to save your custom logo as custom-logo.png file on your computer. It needs to be exactly 16 x 16px in dimensions.

Once you have your custom logo ready, you need to upload it to /wp-content/themes/your-theme/images folder using FTP. If your theme does not have an images folder, then you need to create it.

After uploading you custom logo image, simply add this code to your theme’s functions.php file or a site-specific plugin.

function wpb_custom_logo() {
    echo '<style type="text/css">
    #wpadminbar #wp-admin-bar-wp-logo > .ab-item .ab-icon:before {
    background-image: url(' . get_bloginfo('stylesheet_directory') . '/images/custom-logo.png) !important;
    background-position: 0 0;
    color:rgba(0, 0, 0, 0);
    }
    #wpadminbar #wp-admin-bar-wp-logo.hover > .ab-item .ab-icon {
    background-position: 0 0;
    }
    </style>
    ';
}

//hook into the administrative header output
add_action('wp_before_admin_bar_render', 'wpb_custom_logo');

You can find more information here: http://www.wpbeginner.com/wp-themes/adding-a-custom-dashboard-logo-in-wordpress-for-branding/

function wpb_custom_logo() {
echo '
<style type="text/css">
#wpadminbar #wp-admin-bar-wp-logo > .ab-item .ab-icon:before {
background-image: url(' . get_bloginfo('stylesheet_directory') . '/images/custom-logo.png) !important;
background-position: 0 0;
color:rgba(0, 0, 0, 0);
}
#wpadminbar #wp-admin-bar-wp-logo.hover > .ab-item .ab-icon {
background-position: 0 0;
}
</style>
';
}

//hook into the administrative header output
add_action('wp_before_admin_bar_render', 'wpb_custom_logo');

add this code to your functions.php after uploading your logo (16x16)