None of the blogs will be deleted, but they will no longer be publicly visible, the tech giant says.
People currently posting adult content are advised to either remove it or make their blogs private themselves.
Blogs created after the March deadline may be taken down if they contain adult material, the updated terms state.
Under the updated adult policy terms, nudity will be allowed on Blogger blogs only if it "offers a substantial public benefit, for example in artistic, educational, documentary, or scientific contexts".
Bloggers are already asked to use the tag "adult" if their site contains explicit material, which means a warning page appears before the site can be accessed.
Under its current terms, Google reserves the right to add that tag itself even if the blog author disagrees.
In 2013 the company banned Blogger sites from carrying adverts for adult websites.
Censorship Yahoo-owned Tumblr also adjusted its policies on hosting sexual content in 2013, hiding "adult" themed sites from its search tool but reinstated them after a social-media backlash.
Critics have dismissed Google's move as an unnecessary form of censorship.
"Adult content has historically been at the forefront of fighting for free speech and political dissent, and this won't be changing anytime soon," wrote journalist and sex columnist Violet Blue on ZDNet.
"Sexual and erotic expression is protected speech, and pornography is not illegal."
Culled from BBC News
