I've connected a Calendar from our Sharepoint 2010 site to my Outlook 2010. Calendar items are displayed but I can't see the description field set from the Sharepoint side.
Is there any way to do it?
Outlook only recognizes the standard event item fields. You would need to push the description field into one of those fields.
As long as you are using the standard calendar with no customizations that affect the normal columns, the Description should show up as the body of the calendar event when viewing it in Outlook. If you are not seeing this, I would try creating a new calendar with no customizations. Add some events with descriptions and connect to Outlook.