I have two table,such as:

table1
-----------
id cid
1 1
2 3

table2
-----------
id cid1 parentid
1 1 2
3 3 1

----------------------------------
now! Id is the primarykey,cid and cid1 is foreign key.I want to make table1 and table2 relating with table1.cid = table2.cid1,
please tell me how to write the config file.

Config file? You mean mapping?

http://www.hibernate.org/hib_docs/nhibernate/html/

Part 5.1.11 is about one-to-one