whether "google sketchup" tool is good choose for A7?

But why not learning Blender (free and great tool) , or TrueSpace, or Wings3D ?

But if you have fun using google sketchup, and find it easy (i found it really easy and fun to use also ) ; in their site , it is said it can export to these formats :
3DS, DWG, DXF, FBX, OBJ, VRML, XSI.
A7 can import 3DS, FBX or OBJ formats, so go for it

so say you Blender or TrueSpace or Wings3D are better?

They are not as simple and friendly to use à Google Sketchup,
But they are lot more advanced in terms of modeling.

Try them, and there are really cheap modelers like Silo 2, very complete and fridenly , easy ot use !
And there are also others modeling tools free or cheap i don't have all the list !

"But they are lot more advanced in terms of modeling."
I found google sketchup has a lot of nice tools for modeling buildings, so if that's what you want to do, go for it, that's what it's made for, after all. For more organic shapes, try blender or something else (i like blender most, but it takes time to get used to it).