@Vision Pro Engineer Thanks for your reply and your help! I just copy and paste all of the parameters in your code snippet. But this still not works. I didn't paste the code because most of the component's parameters are set in Reality Composer Pro. You can see that in my attachments.
I am thinking it's about ModelEntity. In my case, "Qiu" is a ball with sphere collision box, but I checked that in my code, Qiu cannot be cast into a ModelEntity. I am thinking probably the Entity itself doesn't have a mesh attached to it, because Qiu is imported from a DCC, it has a child Entity containing a meshResource (but no collision sphere attached to this Entity).
But as the document said, as long as an Entity has PhysicsBodyComponent and a CollisionComponent, it should have the ability to participate physics simulation. Or there must be some misalignment between RealityComposerPro and RealityKit