The invention relates to a Helmholtz resonator. The Helmholtz resonator is arranged on an acoustic pipeline and comprises a cavity and a neck part, wherein the neck part is arranged at one side of the cavity and communicated with the cavity and the acoustic pipeline. The Helmholtz resonator further comprises a sound absorbing structure, wherein the sound absorbing structure is filled in the neck part, the sound absorbing structure comprises a plurality of through holes and is used for communicating the cavity with the acoustic pipeline, the hydraulic diameter d and the porosity phi of the through holes in the sound absorbing structure meet the following relational expressions (1) - (2): the expression (1) and the expression (2) are described in specifications, wherein Re(Zb)apt represents the optimal acoustic resistance value of the Helmholtz resonator, and R represents the reflection coefficient of the downstream acoustic pipeline of the Helmholtz resonator and is a real number; Re(Zb) represents the inlet acoustic resistance of the Helmholtz resonator 10, and the Re(Zb) is the relational expression which is related to the hydraulic diameter d, the porosity phi, the flow resistance and the length of the through holes in the sound absorbing structure 16. The invention further relates to a design method of the Helmholtz resonator.