i contact bittrex some day ago,this is reply:

Thanks for the request. We have a large list of coins but can only launch a few per day. If you would like to see your coin traded, follow us on twitter @bittrexexchange and tweet about how much you like this coin and Bittrex. We respond to creative and insightful posts to help market your favorite coins and Bittrex.

Thanks,
Bill @ Bittrex
Follow us on Twitter: https[Suspicious link removed]xchange

so,every one contact they on twitter.