In this paper, a Z-axis micromachined gyroscope with a new decoupled design was presented. The gyroscope consists of dual proof mass, sense frame and drive frame structure. The sense frame is constrained in the sense direction and anchored on the substrate, which minimize the influence from the motion of the proof mass in the drive direction. The drive frame is also restricted to oscillate in the drive direction. ANSYS has been used to make modal analysis and harmonic analysis to determine the vibration characteristics of the decoupled gyroscope. We introduce the decoupling ratio (ηDtS) of drive mode to sense mode and the decoupling ratio (ηStD) of sense mode to drive mode to determine the decoupling design. The results show that the drive mode and the sense mode are well decoupled.