The Beijing International Book Fair takes place in Beijing every September; the 16th annual Fair will be held this year September 3-7.
Publishers considering attending the fair can find all the background and application information they need at the BIBF website (click the "Overseas Exhibitor" link in the top right for English). This year, in light of general economic conditions and difficulties in the global publishing industry, the BIBF is offering a new attendance option called the Special Publisher Program.
You can download an introduction and application form here, but the upshot is that you can participate in the fair and a large subsection of its activities for around half the price of a regular booth (10,600 RMB as opposed to 19,190 RMB). Check out the introduction for details; the application deadline for this program has been extended to the end of July (this supercedes the deadlines in the application form itself).