Why do you assume a radius of 1.0 would avoid collisions?
What are you trying to achieve?
*Thank you for your reply?
- How to penetrate the model when the operation Character is roaming?
So you want to avoid the character from colliding some other object? like a wall?
In that case you should turn off collisions for the other object.
If you explain a bit more maybe you can get more help 
How to solve The character will fall to the ground after closing the collision.
don’t turn off collisions for the character. Turn off collisions of the objects you want the character to ignore and pass thru.