Abstract: Our understanding of the electromagnetic force, which binds together a proton and an electron to form a hydrogen atom, has given birth to the development of the smartphone as well as cutting-edge information technology. It has revolutionized our daily life. On the other hand, we know little about how quarks and gluons are confined by the strong interaction force within a proton or neutron, or about their complicated dynamics inside a nucleon. Therefore, nuclear physicists around the world have proposed to build a polarized electron-ion collider to further research in this field. The design of the Electron-Ion Collider in China (EicC) as well as several key physics topics will be discussed in this article, as well as the lattice QCD calculation and its importance in nucleon structure studies.