The thermal infrared detector based on Mn-Co-Ni-O thin film is studied. The properties of the detector can be improved by adjusting the thermal conductivity of the substrate. For the thinner detection unit, a new kind of micro-bridge infrared detector is studied. It is find that the responsivity is about 80% higher than that of the nonmicrobridge device, and the detection rate is about 44% higher. This is mainly because its unique structural form reduces the thermal conductivity of the device, and the total reflection effect of light improves the light absorption rate of the detection element. For the thicker detection unit, a polished copper sheet is added to the substrate, which increases the thermal conductivity of the substrate by about 47%, but the response voltage is reduced by about 50%. Therefore, a reasonable choice of heat dissipation copper is required to obtain a suitable time constant and responsivity.