Like the superconductivities in other unconventional superconductors, high-temperature superconductivity in the iron pnictide often emerges after the static antiferromagnetic order has been suppressed, and is always accompanied by strong spin fluctuations. Therefore, understanding the magnetism and its origin could be an important premise for ascertaining the microscopic mechanism of iron-based superconductivity. Neutron scattering, as a powerful tool for studying magnetic ordering and spin dynamics in condensed matters, plays an essential role in understanding the relationship between magnetism and superconductivity in iron-based superconductors. In this paper, we review the neutron scattering results for iron pnictides, including static magnetic structures, magnetic phase transitions, spin excitations and electronic nematicity, and discuss their relationship with superconductivity.