Yes, it is possible. Download the source code and open it in Unity. There is a blender file that you need to edit to create new blocks. You might need to do some configuration in the Unity editor. Let me know if you have any questions.
Thanks for ur kindness.
I tried to import a new model, edit its "Module Prototypes" manually. Create module data and save it.
Return to the Game scene and click initialize, but it can't generate, is there something i did wrong?
You need to keep the first two blocks (solid and empty). Also, you can't generate a castle from just one block, you need to split it into many blocks that fit next to each other. Then you need to set connectors for your blocks. You can read how they work here. In your screenshot, the block has a 0 connector on top and a 1 connector on the bottom. It will only place another block above it that has a 0 connector on its bottom face. But there is no such block in your example.