A method of determining the dynamic Poisson's ratio of a material with a circular solid rod is provided. The method includes at least the following steps. 1. a circular solid rod specimen with the material to be determined for its dynamic Poisson's ratio is manufactured; 2. the length and diameter of the circular solid rod specimen is measured; 3. both the fundamental longitudinal and cross-sectional resonant frequencies of the circular solid rod specimen are obtained through experiments; 4. the dynamic Poisson's ratio of the material according to the formula provided in this invention is calculated; 5. the validity of geometric dimension of the circular solid rod specimen is justified.