Setting up a Google xml sitemap in Magento is fairly simple. You can use Magento’s inbuilt sitemap generation function to handle this.
Here’s how to generate a xml sitemap in Magento:
1. Log in to admin
2. Navigate to System -> Configuration -> Catalog -> Google Sitemap, under generation settings click Enabled -> Yes and Save (enter error reporting e-mails if needed)
3. Navigate to Catalog -> Google Sitemap and click Add Sitemap, give it a name and location (just a slash for public_html root), hit Save & Generate and you’re done
Now you can access your sitemap via http://yourshop.com/sitemap.xml
Remember to submit it to Google Webmasters for better crawl and index rate.