Euler parameters method is introduced to describe the microstructure's rotation behavior in this paper. Compared to the Euler angles method, the Euler parameters method can be used to linearly establish the rotational kinematic equations of microstructure, as a result the simulation computation time can be greatly saved. As a demonstration, an electrostatic torsion micromirror is designed as a netlist composed of beams, plate mass, and electrostatic gaps, whose rotation behavioral equations are deduced with Euler parameters method. The simulation results, such as modal frequencies, of the micromirror agree to that of FEA very well (the relative error within 2.0%), and the transient analysis shows the simulation of model described using Euler parameters method is three times faster than that based on the Euler angles method. All these indicate Euler parameters method is more effective than Euler angles method to describe microstructure rotational behavior, but without loss of simulation accuracy.