In the light of the dynamic characteristics of an inerter, a new fluid inerter is designed. First,the bench tests are carried out on the hydraulic serve exciting platform and the nonlinearities and their effect on the output force are also analyzed. The predicting model of the fluid inerter by the support vector machine is established because the accurate dynamic model of fluid inerter is hard to expressed by analytical methods. Then, the force output of the fluid inerter at different frequency and displacement is investigated, and the variance of the radial basis function and the punishment factor are optimized by means of quantum genetic algorithm. Finally, the comparisons between the results obtained from the predicting model and those of the experiments show that the predicting results are in good agreement with those obtained by the tests. The optimal predicting model has a higher precision, and the amplitude is decreased by 61.36%. The predicting model successfully provides a new method to study the dynamics behavior of the fluid inerter.