Generally speaking, there are three reasons for a high bounce rate:
- Your page is totally relevant to the visitor's query and it answers their question completely, so once they have that answer they simply move on. (Cure: add a strong "call to action" leading visitors to explore the site further.)
- Your page has been artificially "muscled" to the top for a key word when it really isn't relevant to the intent of the majority of people searching using that phrase. They land on the page, discover it doesn't really have anything to do with they're looking for, and leave. (Cure: optimize for other phrases that match your content with searcher intent -- it's better to have fewer visitors, all of whom are truly interested in what you offer, than to have zillions of visitors who couldn't care less.)
- The content of the page is relevant to the search query but is of such poor quality that people leave shortly after landing on the page, to continue their search elsewhere. (Cure: improve the quality of your content. Check spelling, grammar. Make sure you're offering real value, not just a "minimum word count" and a rehash of thousands of other thin-content articles out there.)
In my experience, the third reason is usually the most likely.
Another alternative is that the traffic is coming from some other source (such as some sort of "traffic building" scheme) and not from organic search. This sort of traffic tends to only stay for a few seconds, then leave. Have you segmented your analytics to determine the different bounce rates based on traffic source?