To lower the bounce rate of your web pages
You can improve the bounce rate of your website by improving the content of your website making it more keyword rich and the usability of your web pages. Lowering the bounce rate of your web pages has two major effects for your website it's likely that you will get more visitors and traffic from search engines and your conversion rate will increase.
Bounce rate alone might not be used by Google as a ranking factor but combined with other factors, it could have an effect on the rankings.