In this paper, we propose a design optimization scheme of metal oxide gas sensor with suspended beams. Our design scheme comprises two parts, design of suspended membrane and beam membrane, and design of heater geometry. These processes are based on mathematical analysis. In the suspended membrane and beam design, power consumption at steady state and transient state as well as response speed of microheater are considered. In the heater geometry design, a mathematical method for realizing an arbitrary temperature profile is proposed. After these steps, the electro-thermal performance and the mechanical properties of the suggested designs are investigated by finite element analysis. Here, we demonstrated this scheme for designing gas sensors with two suspended beams. Calculated design operates at 388°C with 7.88 mW power consumption and have uniform temperature profile. In addition, the relation between the dimensions of suspended beams and their mechanical properties has been investigated. By utilizing our scheme, design process of low-power gas sensors satisfying constraints on mechanical properties and footprint can be rapidly obtained.