I have a social bookmarking site in which some members posts adult,dating,drugs related links. Will it treated as violation of adsense program policies?
As I'm sure you're aware that kind of content is prohibited by AdSense. Even though you're not writing it, you have ultimate control (& accountability) for whatever is posted on your site. In the unlikely event AdSense did take an adverse interest in your site they would probably issue a warning first.
This is very risky indeed. Google does not like these types of posts and comments and if they get out of hand, they will shut you down. It is best to just avoid them because its hard to get an adsense account back.