With the aid of photolithography, arrays of one-dimensional porous silicon photonic crystals with the middle infrared mid-gap (λ=5、6、7、10 μm) were fabricated successfully by the combination of microelectronic technique and the electrochemical etching method. For practical use, the roughness of the surface was improved by depositing a Si3N4 thin film with 5000 A°. Then their optical and roughness properties were characterized by FTIR and AFM, respectively. As a result of the synergetic effects rendered by heat isolation and high reflection properties, the array of the one-dimensional porous silicon photonic crystal exhibits feasibility as the substrate for pyroelectric infrared sensor.