i am not able to sync my photos from desktop

Tell us more, satya.

What kind of computer is your desktop? Which operating system are you using?

Usually you sync photos from iTunes, see this link: Sync photos to your iPhone, iPad, and iPod touch in iTunes - Apple Support

https://support.apple.com/HT201313

But this will not work, if you have iCloud Photo Library (Beta) enabled on your iPhone. Disable iCloud Photo Library (Beta) in the Settings for Photos&Camera, if you want to sync photos from your Desktop computer to your iPhone.