Quadricyclane (QC), a kind of strained and caged hydrocarbon, is a potential green high energy density liquid fuel. The pyrolysis experiments of QC (473-1073 K, and 1.0-2.0 MPa) were conducted in a micro-reactor equipped with online GC-MS/FID to understand its high pressure mechanism. It is found that QC firstly isomerizes into 2,5-norbornadiene (NBD) before 598 K under 1.0 MPa with an activation energy of 68.50 +/- 5.95 kJ mol(-1), and then NBD decomposes through three major pathways: the retro-Diels-Alder reaction to acetylene (C2H2) plus cyclopentadiene (CPD), the isomerization into 1,3,5-cycloheptatriene (CHT), and the isomerization into toluene (TOL). The high pressure inhibits the isomerization of QC into NBD and the retroDiels-Alder reaction of NBD, but promotes the isomerization reactions of NBD into CHT and into TOL. The further reactions of CPD and TOL produce small molecules and aromatic products, mainly from the combination between CPD and cyclopentadienyl (CPDyl). Based on the detailed analysis of the decomposition products and kinetics, a possible kinetic mechanism of QC pyrolysis is also proposed.