Will sims 3 work on a Windows 8 Laptop? My laptop is Lenovo G400?

So long as you meet the games required Spec it will work. Sims 3 is compatible with Windows 8, in fact most games work on Windows 8, either as standard or via the compatibility options, which have been around since Vista.

I have my Sims 3 on my Lenovo g400 laptop with specs:
Processor: Intel Celeron (R) 1.90 ghz
Ram: 2 GB

though i have 32 bit Win 7 for OS.
it's quite slow load but playable