Anti?resonance is of great significance in the local vibration control of structures. Generally， the antiresonance frequency refers to the frequency at which the vibration response of a degree of freedom is zero when a structure is subjected to an excitation force. In this paper， a method for computing the antiresonance frequency under multiple excitation forces is proposed. And the antiresonance frequency can also be assigned with the calculation method and methods of partial eigenvector assignment. A linear matrix is constructed with the mass matrix， the stiffness matrix and the excitation force vector， so that the eigenvalue of the linear matrix is the antiresonance frequency under multiple excitation forces. In this paper， the antiresonance frequencies are calculated for a rectangular plate excited by linear surface loads and a spring-mass system under multiple excitations. In addition， the antiresonance frequency of the structures is assigned by structural modification and attaching a simple oscillator. Numerical results verify the accuracy of the calculation method and configuration method.