moved to Managing Data
Santhosh,
Are you trying to export only domains in an Excel sheet?
If you are you can use Domain To Table—Help | ArcGIS Desktop followed by Table To Excel—Help | ArcGIS Desktop in a modelbuilder or python and create a task scheduler to automate this as per your requirement. Scheduling a Python script to run at prescribed times—Help | ArcGIS Desktop
I hope this helps!
~Shan