It is an attempt to characterize of the oxygen penetration depth at the particles scale during chicken manure digestate co-composting wheat straw by Fourier transform infrared microspectroscopy (FT-IRM). It is presented to improve the anaerobic/aerobic co-process mechanism, in order to ensure adequate oxygen supply. The spectral range, spectral resolution and pixel dimensions in the transmission spectra were 750~4000cm-1, 16cm-1 and 6.25μm×6.25μm, and a mean spectrum of 8 scans was used for the second-derivative analysis with nine smoothing points. Chicken manure digestate aerobic composting samples by freeze-drying treatment should be made into 12μm slice by using paraffin section technology. Selection of 2856cm-1, 1640cm-1 and 1568cm-1 , 3001cm-1 was done to represent aliphatic component and aromaticity, respectively, which were used for deciding the boundary of oxygen penetration depth. The difference curve drops rapidly was regarded as the terminal point of oxygen penetration depth. The oxygen penetration depth of chicken manure digestate particles fluctuated within 7~20μm, which was lower than that of pig manure aerobic compost particles. The variation in the oxygen penetration depth can be described by an exponential fitting function. The results indicated that it was feasible to determine the oxygen penetration depth of aerobic composting particles by FT-IRM, but the method and technical parameters should be selected according to the characteristics of different materials.