I have used this code <meta HTTP-EQUIV="REFRESH" content="0; url=http://www.yourdomain.com/index.html"> to redirect one to other, do google recognise the site like one site only?
Well when Google crawls your redirect page it will only find that code so then Google should link both of them together, so I would say yes.
The short answer to your question is yes, Google will recognize a non-deceptive <meta> refresh as the equivilent of a 301 redirect. They have been doing this for four or five years that I know of, but Google representatives have been discouraging this practice recently, so you should only use it if you have no way of having the host server issue the 301 response codes directly. My advice is to use a delay setting of 0, and remove all of the original content from the page and replace it with a simple, direct HTML link to the target page with a brief explanation that the original page has moved. Good luck!
They have been discouraging this method for a long time now. A lot of sites say you should use 301 permanent redirect in .htaccess file. They don't say you can't do it, but they recommend 301 I guess they recognize, count, and update it better. It used to be popular a long time ago, but not so much now. If you do not have access to .htaccess file modifications it might be your only option otherwise go with .htaccess 301 redirecting.