To meet the needs of high performance and microminiaturization of solar irradiance measuring instruments, the key device of absolute radiometerthe micro infrared radiation detection chip, is designed and its theories are analyzed. The bar type diamond with high mechanical performance, high thermal conductivity and high insulation is used for the base of chip. NiP absorbent films that have a high absorptivity in wide spectral range are used to absorb light. The surfaces of nickel-phosphorus black film for infrared absorption have many irregular pores, with the diameters ranging from 50 nm to 10 μm. The reflectivity of NiP films is less than 0.4% at 1.5~16 μm, the transmittance is less than 0.15% at 1.5~16 μm, and the absorptivity is more than 0.99. Thin film resistor is made of constantan which has a good electrical performance. The resistor is prepared by micro-electro-mechanical system (MEMS) technology. The resistance of the thin film resistor is 50.3 kΩ and does not change with temperature, which can meet the requirement of the chip.