Mac comes with a dictionary, but I wonder if there is other free dictionary for mac. Grateful if you would suggest some good dictionary, thanks !!

金山詞霸for mac. i'm using it,very good and totally free.
http://www.chinamac.com/download/44720.html                                                                                                                                                                                                                                                                               

Try this

http://mac.iciba.com/

you can add dictionaries data to the mac OS dictionary....
google it

thanks, let me try doing so tonight