On the basis of the electrical-mechanical analogy theory， the electrical-mechanical-hydraulic analogy theory is further promoted to study the nonlinearity of controllable inerter. A fluid controllable inerter is designed based on the theory of electrical-mechanical-hydraulic analogy. The ideal model and nonlinear equivalent model are established. Some nonlinear parameters are tested by bench experiment. The mechanical output characteristic is analyzed. The results show that the nonlinear factors have a great influence on the mechanical output performance of the fluid controllable inerter， which cannot be ignored. When the compressibility of the liquid cannot be ignored， the inerter characteristic is mainly generated by the inerter under low-frequency excitation. While under high-frequency excitation， the elastic characteristic of liquid helps to suppress the vibration. The results further verify the correctness of electrical-mechanical-hydraulic analogy theory.