How to display an email which include chinese language to display readable language?

It is a tough question. It can be a problem of the email system itself.

It depends on what do you use for email? Foxmail, Yahoo, Hotmail or Gmail?

Short answer:
If you use web-based Yahoo or Hotmail, you may be in better luck.
When you have a encoding/displaying problem for a Chinese message in Yahoo or Hotmail, try every Chinese encoding one by one. Of course, if you know the sender is from China, you can start with Chinese Simplified (GB2312) first, then Unicode (UTF-8).. if from HK or TW, then try Chinese Traditional (big5)...

How? For Firefox/Netscape, go to View, then Character encoding, then the right encoding ( you may need to go to "More Encoding", then "East Asian" first.

If you are using Gmail, you can't read non-Unicode(GB or big5) Chinese messages. You have to forward the message from Gmail to your own Yahoo or Hotmail account to read them.

A general solution as I wrote at Khuang.com: put your Chinese text in Word or PDF document and attach it in your email or you may even put then in graphic format such as gif or jpg if you know how. Ask your sender do the same if you cannot read their Chinese content. If they don't even have Microsoft Word, ask them use the WordPad in the Windows Accessories

More details may be found the link I put the following source.
Or just email me for further assistance.