composer require magento/product-community-edition 2.1.0 --no-update
composer update

Problem 1
- The requested package magento/product-community-edition could not be found in any version, there may be a typo in the package name.
Potential causes:
Read https://getcomposer.org/doc/articles/troubleshooting.md for further common problems.
@zhiyicai
Thank you for reporting this issue!
Please, check you composer.json for this section:
"repositories": [
{
"type": "composer",
"url": "https://repo.magento.com/"
}
],
I have checked them,existence the code,but is still not upgrade.
Possibly related issue #5275
@zhiyicai Could you please check the proposed solution under the published a Technical Bulletin to address this issue.
http://devdocs.magento.com/guides/v2.1/release-notes/tech_bull_tls-repo.html
@zhiyicai According to contributor guide, tickets without response for two weeks should be closed.
Please feel free to reopen if it's needed.
Most helpful comment
@zhiyicai
Thank you for reporting this issue!
Please, check you composer.json for this section:
"repositories": [ { "type": "composer", "url": "https://repo.magento.com/" } ],