I use this link and work.
lv_obj_t * first = lv_obj_create(NULL, NULL);
lv_scr_load(first);
/* Later /
lv_obj_t * prev = lv_scr_act(); / save previously active screen /
lv_obj_t * second = lv_obj_create(NULL, NULL);
lv_scr_load(second);
lv_obj_del(prev); / prev is now not the active screen, so it can safely be deleted */