//如果你创建定时任务的函数是这样的则这样移除

//wp_schedule_event( current_time( 'timestamp' ), 'twicedaily', 'my_new_event' );

wp_clear_scheduled_hook('my_new_event');

//或者是这样的

//wp_schedule_event( current_time( 'timestamp' ), 'twicedaily', 'my_new_event', array( 'some_arg' ) );

wp_clear_scheduled_hook('my_new_event',array('some_arg'));