Some one is copy my website's content on his blog ?

[Magnus]

Some one copied my website's content on his blog. Please tell me what to do ?

[Jake]

Send them a note indicating you identified the theft of content, requesting they remove the material, often they will comply.
You could threaten to contact their hosting company as a next step.

It's probably not worth the expense to take any real legal action, which typically wold start with a cease and desist order? from a lawyer.

Search engines tend to give the first (original) source of the material preferred search ranking.

[Richard]

There are more advanced ways to protect against scraping and copying, but none of them are entirely foolproof. You should expect that the more popular and visible your site gets, the more often you'll find your content scraped and re-published. Many times, you can ignore this problem, but if it gets very severe, and you find the scrapers taking away your rankings and traffic, you may consider using a legal process called a DMCA takedown.

Check out: Four Ways to Enforce Your Copyright: What to Do When Your Online Content Is Being Stolen