Fast tool servo (FTS) cutting has the superiority of high efficiency and high precision, which has attracted great attention from the field of microstructure machining. 3-degree-of-freedom (DOF) FTS device driven by piezoelectric (PZT) actuator, with high frequency, high precision, and low crosstalk property, are quite appealing for realizing complex microstructure machining. Therefore, a novel 3-DOF piezo-actuated FTS mechanism with high natural frequency and decoupling property is proposed in this paper. First, the static and dynamic models of the mechanism are established by using the compliance matrix and Lagrange equation methods, respectively. Then, the structural parameters of the mechanism are optimized by the genetic algorithm (GA) based Pareto multi-objective optimization algorithm. With the purpose of verifying the property of the above approach, the finite element analysis (FEA) acting on the designed mechanism has been carried out. Moreover, the modeling tasks in terms of cutting principle and trajectory planning are demonstrated in detail. Besides, a series of tests are carried out to verify the performance of the developed 3-DOF FTS. The testing results indicate that the working stroke of the mechanism is up to 40 μm, the natural frequency is above 873 Hz, and the mechanism has excellent motion decoupling performance (within 2%). The error of the trajectory tracking in all three directions are kept within ±0.7 μm. Finally, compared with the desired surface, the error of the machined microstructural surface is kept within ±1.5 μm, which further verifies its satisfactory performance towards ultra-precision FTS machining of microstructure.