Will Google penalise me if I have same content on two domain name. One domaine is .com and one is co.uk.
How are the domains running? Seperate servers or IPs? I would be tempted to use mod rewrite and redirect the .co.uk traffic to the .com.
Why do you need 2 sites? My advice would be to 301 one site to the other. Find which is the best site in terms of age, backlinks and rankings and choose that one.
My main reason I want use two domain name is, i get most of visitors from google.com for the com domain. If I also have .co.uk domain, i will get visitors from google.co.uk Will this work?
This is not the case. A .com works just as well in the UK as a .co.uk - its the location of the web server that matters. You should only have one version of the site and redirect the other one to it.
I was in the same situation with a .com and a .net .. they were both on the same ip and everything, but just to be safe I 302'd the .net, and everything is still running fine
I've owned a .com since 2002 & then in 2003 after an awful time with a webhost who I'd also registered the name with I changed over to .com.au. The reason I kept the .com was a friend runs a sub-domain from that site, and as he's located in England it would be a little funny having a .com.au address. Until recently I ran both sites with the same content. However, after I put Adsense on my site I was worried I'd be violating the google TOS & didn't want to risk it. So I've pulled all the content from the .com site & just set up an error page, with a link to the .com.au address. I haven't been penalised for having duplicate content on both sites.
I would argue that it wont hurt both of the sites. It will probably just hurt one of the sites. If google sees the content as duplicate than it will just ignore one of them.