Abstract: With the help of Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy(XPS), based on a modified six-cylinder heavy-duty diesel engine, this paper studied the different start of injection (SOI) and the premix ratio(R_p) under the n-butanol/diesel reactivity controlled compression ignition（RCCI）soot particle of chemical characteristic, and compared with the conventional diesel combustion（CDC）model contrast research, The main conclusions are as follows: the advance of SOI and the increase of R_p lead to an increasing trend in the relative contents of aliphatic C－H functional groups and oxygen-containing functional groups. Under the same SOI, the relative contents of aliphatic C－H functional groups and oxygen-containing functional groups in RCCI mode are higher than those in CDC mode. It is worth noting that the content of C－OH functional groups is higher than that of C＝O functional groups in CDC mode, while the opposite result occurs in RCCI mode. O/C increases slightly with the increase of R_p. The O/C of RCCI mode is higher than that of CDC mode, and the changes of SOI have no obvious impact pattern on O/C. For the hybrid form of carbon atoms, the change of SOI and R_p has little effect on sp³/sp², while the change of combustion mode has great effect on sp³/sp².