Urgent help needed on divorce!

Hi everyone, I came to the United States several years ago in F2 visa. But my ex-hu*****and went back to China long time ago without any notice, I don't have any information about him anymore. Now I want to marry again. But I need divorce as soon as possible, but I cannot locate him now. How and where I could I get divorced faster and easier. Should I file it in US or China? Which way is faster? Any suggestion or experience sharing is highly appreciated! Please advice!