Aiming at the pyrolysis and coking of RP-3 aviation kerosene at temperatures above 1 000 K and ambient pressure around 1.8 MPa，optical imaging and time series sampling of RP-3 aviation kerosene soot formation process under oxygen-free environment were conducted by using a new sampling method to study the formation rate and morphology evolution route of soot. The results of optical imaging indicate that the higher the ambient temperature，the faster the growth rate of soot and the higher the peak soot mass. By comparing the transmission electron microscopy images of soot at different times，it is found that soot could complete the whole process from fuel pyrolysis to mature aggregate formation within 8 ms at 1 200 K. After the soot matured，the particle size distribution and internal structure no longer change over time. However，even though the total mass of soot has stopped increasing，the average particle number of soot aggregates continues to increase with time.