Voice coil motors (VCMs) are becoming more popular due to their small size and high dynamic performance. They are commonly used in hard disk drives and vibration isolators in optical systems. Torque ripple is an important performance index for rotary VCM. In order to reduce torque ripple and make their dynamic performance better, various parameters of two different rotary VCM topologies are studied with finite element analysis. The effects of magnet separation angle, coil separation angle and coil type on torque characteristics are analyzed. In order to achieve better dynamic performance and higher precision, optimization study is conducted to find optimum design, which has only 3.3% torque ripple throughout its whole operation range.