In seo we are doing article submission .same article submitting in many site..this is an dulicate content? why google ignore this type of seo promotion?
Yes, submitting the same article in many sites will be treated as the duplicate content so if you want to get beneficial results in the terms of quality back links and traffic then it will be good if a unique article to be submitted in only one article site.
After panda update Google doesn't entertain such kind of stuff. You can spin your article and submit it in to different article directory site.
Yes, Alan you are right. Submitting same article in various article directories will be treated as duplicate content by Google, although submitting one article per website is quite difficult and hence you can opt for submitting same article to 2-3 different websites.
It will be a good idea to submit unique articles on each directory and also choose the top 2-3 of these so that it will be easy for you to spin just 2-3 versions or the article.