1956 in may, with the assistance of the former Soviet union, heavy water reactor and cyclotron started construction in the suburbs of Beijing. Reactor is a device to realize large-scale controllable nuclear fission chain reaction and provide nuclear energy to human beings. Accelerator is a device that artificially produces high-energy particles and uses them to smash atomic nuclei. It is the most important tool to study the complex structure inside the nucleus. 1958 On September 27th, China's first experimental atomic reactor and cyclotron were officially put into operation. The completion of the atomic reactor and cyclotron marks the entry of China into the atomic energy era. The life of the reformed heavy water reactor is far longer than the original design of 15 years, and it is still playing an important role.