Designed to lift space station components, deep-space probes and communication satellites into orbit, the Long March-5 Y2 is Beijing's second heavy-lift rocket able to carry up to 25 tonnes -- or around the same weight as 16 cars.
It will take off from the Wenchang launch center in the tropical island province of Hainan, carrying the new Shijian-18 experimental communications satellite, state broadcaster CGTN reported Saturday.
It said the satellite will operate on geosynchronous orbit and provide communications services over China's territory -- boosting internet access and providing access to more television channels.
The process of filling propellant into fuel tanks began Saturday afternoon, CGTN said.
Beijing sees its multi-billion-dollar space programme as a symbol of its rise and of the Communist Party's success in turning around the fortunes of the once poverty-stricken nation.
Last month it successfully launched the Long March-4B, its first X-ray space telescope to study black holes, pulsars and gamma-ray bursts.
And in April, the country's first cargo spacecraft completed its docking with an orbiting space lab -- a key development toward China's goal of having its own crewed space station by 2022.