The extensive production of alternative fuels from renewable biomass sources through microbial fermentation has attracted wide attention, which is a large-scale and targeted means to meet various application conditions. As an alternative terpenoid hydrocarbon fuel produced by this renewable means, there is a large application prospect for cycloalkane p-menthane (1-isopropyl-4-methylcyclohexane, PMT). In this work, the atmospheric pyrolysis performance of PMT was investigated by the pyrolysis experiment under 773-1023 K in a tandem microreactor and GC-MS/FID online detection system. The emphasis of this work is to comprehensively analyze the pyrolysis mechanism of PMT, with a detailed reaction kinetic model (294 species and 1862 reactions) proposed. Besides, we preliminarily discuss the pressure dependence of PMT pyrolysis between the atmospheric data and newly investigated high-pressure data at the same temperature and residence time. The model well reproduced the experimental product distributions under both of the pressures. It is found that the side chain scission of PMT served as chain initiation reactions including the isopropyl scission and methyl scission, which contribute much to the consumption of PMT according to the sensitivity analysis. Those unimolecular decomposition reactions more easily occur under low pressure and have greater contributions to the fuel consumption. The H-abstraction reaction takes the largest proportion in the consumption paths of PMT benefiting from the massive generation of small groups. The ring-opening reactions of the generated radicals and the subsequent reactions produce a large number of branched alkenes and conjugated dienes, such as 3-methyl-1-butene, 2-methyl-1,3-butadiene, etc. Aromatic products are mainly benzene and toluene, the formation of which is mainly through C5 cyclic and C6 cyclic precursors. This work aims to provide a reference for understanding the pyrolysis behavior of multibranched cycloalkanes and cyclic terpenoids.