The optimized structure of CO2 gas sensor has been simulated consists of low cost components and easy for fabrication. The structure is based on reflective type gas cell using aluminium material. Optimization was made on radius of aluminium surface to enhance the performance of the sensor. The results show that the gas sensor is fully optimized and able to detect higher power efficiently. It is proven that the optimized CO2 gas sensor of 8-Multiple-Input-Single-Output (MISO) has capability to gain power of at least 1.0 Watt with 12.5% efficiency. However, Single-Input-Single-Output (SISO) has shown greater efficiency as it can detect 29.1% of total power supplied with the lowest Merit Function (MF) value of 0.648.