How to scene.add many children objects in a big model

[vocal copper]

I try to scene.add(gltf.scene.children[0],...) but it's faild. Tks so much

[paper pendant]

if you want to just add every child, just do scene.add(gltf.scene)
if you want to add specific children, it should work fine the way you wrote it.
see example:
https://codesandbox.io/s/billowing-tree-nf284t?file=/src/index.js