A Long March-4B rocket carried the 2.5-tonne telescope into orbit from the Jiuquan Satellite Launch Center in northwest China's Gobi Desert at 11:00 am (3:00 GMT), according to the official Xinhua news agency
The Hard X-ray Modulation Telescope (HXMT), named Insight, will allow Chinese scientists to observe magnetic fields and the interiors of pulsars and better understand the evolution of black holes.
It will also help scientists search for gamma-ray bursts corresponding to gravitational waves and study how to pulsars can be used for spacecraft navigation, Xinhua said.
"Insight is expected to push forward the development of space astronomy and improve space X-ray detection technology in China," Xinhua 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.
In April, China's first cargo spacecraft successfully docked with an orbiting space lab -- a key development toward China's goal of having its own crewed space station by 2022.
Last month, China opened a "Lunar Palace" laboratory on Earth to simulate a moon-like environment and house students for up to 200 days as the country prepares for its long-term goal of sending humans to the natural satellite.