Tumblr's Mega Editor is a Web-based editor that helps you manage all posts on your blog with ease. You can use it to delete all your Tumblr posts in mere minutes, instead of deleting each post manually. You can access the Mega Editor only after you log in to your Tumblr account. Note that deleting Tumblr posts is not a reversible action; you can't recover deleted posts.
Erase All Your Posts
Navigate to the Mega Editor page (link in Resources) and log in to your Tumblr account if prompted to do so. All of your blog posts are displayed on a single page. Click each blog post until you select all of your posts. When you select a post, a white check mark appears in its upper-right corner. Click the "Delete" button to delete all selected posts. Click "OK" to confirm only if you are absolutely certain you want to delete the posts permanently. To deselect posts, click the "Unselect" button.