This advisory was just sent to us by CITS, the local travel service:

民航总局严格手提行李规定
New Regulation of Carry-on Luggage

根据中国民航总局的规定，５月１日开始，在国内航班上持头等舱客票的旅客，每人可随身携带两件物品；持公务舱或经济舱客票的旅，每人只能随身携带1件物品。每件物品的体积均不得超过20×40×55厘米，上述两项总重量均不得超过5公斤。

According to CAAC , new regulation of carry-on luggage will be launched effective from 01May. Base on this regulation, on domestic flights, first class travelers can take 2 pieces carry-on luggages, whilst business and economy class travelers can only take 1 piece.The size of each luggage should not exceed 20 x 40 x 55 cm, and the total weight of these carry-on luggage should not exceed 5 kg.

Imagethief can't imagine anything more traumatic for China's air travelers, who suffer the dual curses of lack of faith in the baggage-checking system and partiality for large carry-on items. As a regular domestic traveler, Imagethief long ago gave up trying to carry on even a modestly-sized trolley-bag. The life-or-death struggle for overhead bin space was reminiscent of the carnage one normally associates with African water holes and nature-red-in-tooth-and-claw documentaries. Now I limit myself to whatever I can cram under the seat in front of me.

Fortunately, my bags have always made it out the far side. But this will be a painful adjustment for legions of Chinese business travelers accustomed to trying to cram steamer trunks, cargo containers and live Afghan hounds into the overhead bins. 

If, that is, it is enforced.

Previously:

Stewardess, my elephant won't fit in the overhead compartment (October, 2005) 

Covered Wagon ain't Air China 

We wuz gonna fly Air China...