Abstract: B-COPNA resin, synthesized from the light fraction of ethylene tar (ETLF), is a superior precursor of the carbon materials. An in-depth understanding of the COPNA resin preparation process and strict control of crosslinking degree are crucial for controlling carbon materials performance. Therefore, the synthesis kinetics of B-COPNA resin prepared from ETLF was investigated using in-situ FTIR in this work. The synthesis kinetic models of B-COPNA resin were established for the first time. To express the kinetic model, the concentration changes of C–H in aromatic rings and O–H in PXG monitored by in-situ FTIR were selected as two indicators to calculate concentration of other compounds and describe the synthesis kinetics. Then confirmatory experiments were conducted, and the ρ2 (>0.9900), F-values (>10F0.05) and parameter errors (below 3%) of kinetic models verify that concentration changes of C–H and O–H can be used to describe synthesis kinetics of B-COPNA resin. Based on the results of confirmatory experiments, the synthesis kinetic model of B-COPNA resin in the ETLF system is established successfully using concentration changes of O–H as an indicator, whose appropriateness and feasibility are proved by the ρ2 (0.9960) and F-values (>10F0.05). These models could accurately describe the synthesis rate of B-COPNA resin.