finally, i have fix this problem…
i can delete the child actor component in blueprint editor now, i don’t know which action makes it works. i just try to modify the actor class and the child actor class again and again.
then i can delete the child actor component, but it still lots of duplicated components in the map. then i delete all instance in the map(the instance of child actor component can not select in the map, click it will select the whole actor, that’s ok), everything works pretty good now.
the three child actor component have the same times of duplicate instance in the map, it seems not operated by human (like shift + drag to create duplicated instance). but i can not find more info to you. sorry.