In recent years, various fields have established an urgent need for real-time online measurement of infrared spectra. To this end, reducing the weight and size of infrared spectrometers is particularly important. This paper reports a micro-optical element static Fourier transform spectrometer (MOESFTS) with a working wavelength from 3.7 µm to 4.8 µm. This spectrometer is entirely composed of micro-optical elements, and its interference system comprises stepped micromirrors and a lightweight beam splitter to realize a lightweight, miniaturized instrument capable of static real-time spectrum measurements. We establish a field-of-view integral model of the interference-image point intensity to analyze the influence of the field of view on the reconstructed spectrum. A prototype was designed and constructed, its micro-optical elements and systems were optimized, and spectral calibration was completed. The spectra of acetonitrile (CH 3 CN) and carbon dioxide (CO 2 ) were measured, and the peak drift errors were found to be less than 0.18%. Our experimental results show that the MOESFTS system can be used for real-time online spectrum measurements of liquids and gases.