"An anomaly occurred during the flight of the rocket", Xinhua reported, after the rocket blasted off from the southern island province of Hainan.
"Further investigation will be carried out", the Xinhua report said.
The next Long March 5 launch was scheduled for November, carrying the Chang'e-5 spacecraft. The heavy weight rocket was due to carry the heaviest Shijian-18 satellite and was to launch China's next mission to the Moon.
It is not yet clear what caused the rocket to fail.
Rocket carrying 7.5-tonne experimental satellite was to help Beijing launch a lunar probe later this year.
It is created to carry a payload of 25 tonnes into low Earth orbit and 14 tonnes into GTO.
It was not immediately clear how Sunday's failure will affect planned missions.
With a weight of 7.5 tonnes, Shijian-18 is China's latest technology experiment satellite and the heaviest satellite China has ever launched into space.
The Long March-5 Y2 was fuelled with liquid hydrogen, kerosene and liquid oxygen and the process of filling propellant reportedly began from Saturday.
Beijing sees its multibillion-dollar space programme as a symbol of China's rise and the Communist Party's success in turning around a once poverty-stricken nation.
The European Space Agency's Ariane 5 rocket suffered four failures and partial failures in its first 14 launches, but has since put together 80 successful flights in a row.
China is carrying out massive space programme in recent years with missions to moon and manned missions to build a space station which is now under construction.