There are three reliable web sites I use when researching flights to China. I have purchased from each of them and had no problems whatsoever. Prices do vary between each though, so check and compare.
I use Elong and Ctrip for purely domestic flights, usually from Shenzhen SZX. Travelzen I use for domestic and from HKG.
Elong is a subsidiary of Expedia and fairly straightforward to use.
You need to enter a lot of information to use a foreign credit card. However, it seems you don’t need to fax them a copy of the actual card anymore, which I did a few years back when I first used them.
Elong has a handy dandy 30 day calendar of cheap fares too.
Ctrip is probably China’s most famous online agency and been around for awhile. I don’t find it quite as easy to use compared with Elong however.
Ctrip has an archaic process for dealing with non-mainland credit cards, time to move into 2012 Ctrip. I particularly like how they are protecting you, their customer, by asking you to send actual images of your card, both sides, AND a signature. I’m sure I trust the person looking at these images as over an online encrypted connection. In any case, I did this a few years ago and haven’t had non-authorized charges to my card.
Payment with non-Mainland Chinese credit cards
To protect our customers from possible international credit card fraud, we may require additional verification from cardholders paying with non-Mainland Chinese credit cards. When paying with an international card, be prepared to provide the following:
1) Completed & signed Authorization Agreement
2) Images of credit card to be used (front & back including cardholder signature)
3) Image of cardholder’s passport signature page
Customers can digitally photograph or scan the above. Email: firstname.lastname@example.org (domestic flights) or email@example.com (international flights). Fax: 86 21 5218 9073 (domestic flights) or 86 21 6239 6939 (international flights).
Ctrip’s fare calendar doesn’t have as many dates as Elong, so I find myself scrolling a bit sometimes, but still nice to have.
Travelzen is the newest of the three and I think the easiest to deal with for non-mainland credit cards.
The biggest drawback for this site is the lack of a fare calendar. On the plus side, using a foreign credit card is simple and doesn’t require any scanning.
My suggestion when looking for the most competitive price is to check all three, and compare. I think you’ll be hard pressed to find a ticket less than what is on these sites.