Hey @liu_zeren!
You can refer to this post of mine on the same exact topic for a detailed explanation.
When it comes to your specific use case here:
While you can make a character walking on walls & ceilings using the Character class, since you mentioned this:
I’d assume the movement mechanics you have in mind won’t align with the character movement component.
But…
then how will that work exactly? 
The issue is not only about the Pawn class, let’s say we’re using a Character class. But still, how would you handle the surface alignment that way?
It’s ok tho, as you can just make your animations in place by disabling the Enable Root Motion property and enabling the Force Root Lock property.
In conclusion, you’ll wanna go with a pawn class in this case.
I’d also recommend checking out these tutorials on creating a pawn that walks on all surfaces! The first one here is about setting up the basic movement and animations, and the second one here is about the orientation logic.
Hope this helps! 