i have a website contains 4 hundred thousand pages. website is submitted in web master tools. site map is uploaded and everything seemz to be pretty fine. but out of 4,00,000 pages only 8000 pages are indexed, i need to know that what could be the problem
Not enough information. It could be any number of things. You could encourage G to index the pages by deeplinking to parent categories within your nav tree. Just a thought
Before answering this question i would like to ask you that how many days ago you have submitted your site map in Google webmaster tool. Actually for such a huge site it's better to have more than one site map and then again one final sitemap having list of those previous site maps. As it is suggested to list 1000 pages per site map. So unless I know the way in which you have build the sitemap and time period of you sitemap submission i can say the exact possible reason.
my site maps are divided into different parts. each sitemap contains 35,000 pages. i submitted this whole sitemap a month ago
The deep crawl occurs once a month, at that point in time, it will index all the urls it knows about.
Google doesn't list all its indexed pages. Some deeplinking will help, also; I'd recommend building more backlinks so that your indexed pages can rank well on the engines.