I found I can manually change editor camera by this way:
func geteditorcamera(camera_index):
var e = get_editor_interface().get_editor_viewport()
var cam = e.get_child(1).get_child(1).get_child(0).get_child(0).get_child(cam_index).get_child(0).get_child(0).get_camera()
return cam
If the function not work,you can use code below to check(new version godot change the camera hierarchy)
# var root = e.get_parent()
# var all_nodes = []
# var c = root.get_children()
# while !c.empty():
# var child_list = []
# for i in c:
# child_list += i.get_children()
# all_nodes += child_list
# c = child_list
# for node in all_nodes:
# if node.get_class() == "Camera":
# print(node.transform)
# print(node.get_path())
# for i in range(deep):
# node = node.get_parent()
# print(node.get_class() + str(node.get_index()))
# print(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>")