Hello, a picture of moon shot by my phone, no any modification. why rejected?

Hello.

There are a few issues. You have 'banding' in the sky—you can see the transitions in the colour.

Lens flare as well...

Plus composition is another point to consider.

It would be a good idea to learn a bit about photo editing.

Stock already contains 7.6 MILLION moon images. This is what you're competing with:

https://stock.adobe.com/search?k=moon

This might be OK for posting on social media, but it's not suitable quality for commercial use-- print, digital or textile. 

Read your Contributor User guide for tips on what Stock expects. All digital photos require some editing. 

• https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
• https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html
• https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/photography-illustrations.ug.html
• https://helpx.adobe.com/stock/contributor/help/how-to-submit-distinct-content.html
• Model/Property Releases:
  https://helpx.adobe.com/stock/contributor/help/model-release.html
  https://helpx.adobe.com/stock/contributor/help/property-release.html

Good luck!

Because you did not edit the picture to make it suitable for stock. But it looks like the moon is too detailed. Samsung is known for embellishing pictures like this...internally.

The moon is overexposed. There is a light flare. The building is crooked and does not belong in the shot.