I usually have my Chrome synced with my Gmail, which does all the synchronization.
So even if I uninstall it, the reinstalled version automatically loads the previous bookmarks after logging in from my Gmail.
Anyway, if by outside you mean as an external HTML file then it's easy.
Open the Tools menu (the drop down button on top right), hover your mouse arrow over the Bookmarks button and click on "Bookmark manager". There, you'll see a drop down option called "Organize" (top left side). Click on it and then select the very last option, which is labelled as: "Export bookmarks to HTML file...". Name it and save wherever you want to save it. Now even if you re-install the browser, just go the same organize option and instead of export, click on the import button and select the file that you saved a while ago and load it. You're done. =)