I tried to do that 6 months ago, but till now I didn't get any reply from Dmoz about 'Why I can't be listed in or how to make it through'. Is there anyone can tell me more about that?
The best advice is to read the threads on this very page. It will save so much time in typing it all again The answer to your question is plain to see.
You need to try again! Just make another submission and I think you might have chosen wrong category before so that you could not do that. Try this time with everything correct! You will definitely have luck!
What? Even though the submission guidelines say to choose the one best category and suggest your website just once? In practice, one extra listing suggestion some months after the first won't get you branded as a spammer. Frequent suggestions to several different categories will.
The key is to make sure your site is quality and unique. Even if you have a good site, if it doesn't add any additional value to the sites already in DMOZ for that category, chances are you'll be rejected. You need to add value, and your site will speak for itself and get approved.