您可以筛选\'get_avatar\':

add_filter( \'get_avatar\', \'wpse_67657_new_avatar\', 10, 5 );

function wpse_67657_new_avatar( $avatar, $id_or_email, $size, $default, $alt )
{
    // create a new img element or …
    $new = str_replace( \'s=40\', \'s=80\', $avatar );
    $new = str_replace( \'avatar-40\', \'avatar-80\', $new );
    $new = str_replace( " height=\'40\' width=\'40\'", " height=\'80\' width=\'80\'", $new );
    return $new;
}