High-pressure thermal decomposition :of tetrahydrotricyclopentadiene (THTCPD) and binary high-density hydrocarbon fuels of JP-10/THTCPD were investigated at 500-660 degrees C and 4.0 MPa in an electrically heated tubular reactor. The decomposition of THTCPD under high temperature, high-pressure, and low residence time was conducted to analyze their effects-on the products. The experimental results of JP-10/THTCPD pyrolysis show that the THTCPD pyrolysis is greatly easier than the thermal cracking of JP-10, and the addition of JP-10 can-Significantly promote the THTCPD, pyrolysis, which is evidenced by the fact that THTCPD conversion increases up to -80% at 660 degrees C when blended with 50 JP-10. It maybe ascribed to possible reason about the pathway and mechanism of JP-10/THTCPD' pyrolysis is that the free radicals generated by the decomposition of THTCPD help to promote the decomposition of JP-10 via H-abstraction reactions.-Correspondingly, a large number of new free radicals generated: from the JP-10 pyrolysis could also-react with JP-10 and THTCPD, which is helpful to promote the decomposition of THTCPD via H-abstraction reaction. Besides, the contribution of THTCPD to JP-10 could also explained by the chemical equilibrium,point of view, since JR-10 is one of the products of THTCPD. Meanwhile, the-thermal isomerization pathways of THTCPD, are also slightly changed in the presence of JP-10. Our, experiments could provide necessary, information for the potential applications of THTCPD fuels in advanced aircraft.