When I start Kdevelop, something is causing my whole project to recompile, but none of files has been changed.
Is there any option I can disable ?

Do you use cmake? KDevelop runs cmake with a special generator flag to get some information (esp. include paths and compiler defines). Maybe that causes it to be rebuilt?

No, its autotools.
I just checked after opening kdevelop most of directiories modification time is changed and some C files modification time.
But nothing was changed.

That project file browser shows files strangely slow compared to 4.7, maybe its it.

EDIT: i disabled all extensions but still my whole project wants to recompile

Very strange, I'm not aware we touch files in any way, except maybe through some version control system. Which project manager do you use? Can you try to re-import the project using the Generic manager? That one quite certainly does nothing fancy.

It was KdevCustomMakeManager ( something like that, I removed *.kdev),
reimported project as KDevCustomBuildSystem
and works perfectly.
Thanks.