Abstract: Uncooled infrared detectors are widely used in both civilian and military applications. Recently, new two-layer microbolometers with improved performance were developed. Finite element analysis and optical admittance matrix calculation were used to study the main properties of such two-layer microbolometers. The simulation results revealed that compared with the conventional one-layer microbolometers, the new two-layers microbolometers exhibit improved performance under the same conditions. In addition, the thermal property of S-type two-layer bolometer is excellent. However, the stability of S-type two-layer bolometer is poor whose structure is very difficult to be fabricated practically. Although the temperature rise for U-type two-layer bolometer is not so good as that for S-type bolometer, the thermal property of U-type two-layer bolometer is significantly better than those for the traditional one-layer bolometers. Particularly, U-type two-layer bolometer exhibits better light absorption, mechanical stability and device manufacturing, compared with those of S-type two-layer microbolometers. Therefore, the optimal integrated properties U-type two-layer bolometer shows is much better. In addition, a new U-type two-layer bolometer with better comprehensive properties was designed.