Who know which casing suitable for it?
Prefer the small and flat top design one.
thx

Not sure what you mean by "flat top" But personally like this one:
http://www.jonsbo.com/en/products_17_1.html



With room for 175mm CPU cooler it will fit Hyper 212 cooler no problem.

flat top mean like Silverstone Lascala etc...

Other brand have?

Hmm, horizontal casing to fit standard height cooler and small size, a little tough. All I see are 25mm-30mm shy on height requirement.
Sorry can't help.

Mostly ended up as a square cube style instead, if you can take that type.
There are many over at Lian-Li, aside from Jonsbo / SilverStone aluminium casing builders.

Like their new casing below, but not sure when will hit local market.

That shape also can, which Silverstone model fit this cooler?

Silverstone : FT03 (not sure if I should call that a cube at all) but not flat on the top if that's part of your requirement
Jonsbo : W1, stock easily available locally.
Lian-Li : PC V359, PC Q36, PC Q33. Stock, probably hard to find here (first two models are completely new).
Others: Corsair Carbide Air, Fractal Design Node 804. Both easy to be found.

Unfortunately not all cube fits a huge tower cooler, still depends on their internal layout design.
There are some that looks kinda decent size from the outside such as Lian Li PC V355 but internal layout just not allowing bigger CPU cooler.