Immune system acts as a natural barrier and kills pathogenic organism that can cause infection. However, dysregulated immune response may lead to many diseases and even death. In this article we will discuss the immune response against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and understand how a complex of protection measures, including mechanical barriers, innate and adaptive immune responses, coordinate and combat against pathogenic elements. Meanwhile, coronavirus infection might elicit overreactive immune reactions, called cytokine storm, resulting in overwhelming inflammation and even death. We will also briefly discuss the challenges and difficulties in human coronavirus vaccine development due to the antibody-dependent enhancement effect.