你必须通过$defaults
作为第二个参数add_theme_support()
根据Codex
$defaults = array(
\'default-color\' => \'000000\',
\'default-image\' => \'\',
\'wp-head-callback\' => \'_custom_background_cb\',
\'admin-head-callback\' => \'\',
\'admin-preview-callback\' => \'\'
);
add_theme_support( \'custom-background\', $defaults);