Taking the surrogate fuel (64% ethylene and 36% methane in mole percentage) for regenerative cooling pyrolysis products used in HIFiRE-2 scramjet combustor as an example, present work systematically explores the workflow of the integrated mechanism reduction for surrogate fuel of pyrolysis products, the kinetic performance verification of the preferred reduced mechanism, and the combustion simulation application of the reduced mechanism in scramjet combustor. A static integrated reduction strategy is performed to obtain reduced mechanism for the surrogate fuel with the NUIGMech1.2 as detailed mechanism under wide conditions for temperature range of 900 - 1800 K, pressure range of 1 - 4 atm, and equivalence ratio range of 0.25 - 5.0. A reduced mechanism (34 species and 181 reactions)with remarkably reduced size is obtained, which presents favorable performance incomprehensive kinetic validations. With this compact and high-fidelity reduced mechanism, the combustion simulations for the scramjet combustor are carried out combining with tabulation of dynamic adaptive chemistry for run-time speed-up. The simulation results of static pressure profiles obtained for cold and hot states match well with the experimental measurements for the two conditions with flight Mach number of 5.84 and 6.50. Meanwhile, the flow and combustion characteristics of the two conditions are investigated based on simulation results. The integrated reduction strategy and systematic kinetic verification used in present work provide reference values for the application of more complex surrogate fuel mechanisms in scramjet combustor combustion simulation.