Endothermic hydrocarbon fuels undergo thermal cracking before entering the combustion chamber and can produce a mixture of unreacted fuels and pyrolysis products (i.e. cracked fuels). The objective of this work is to investigate the effects of pyrolysis conversions, pyrolysis pressures, ignition pressures and free radicals on ignition characteristics of cracked n-decane over temperature of 1300-1800 K, pressure of 0.1-3.0 MPa and equivalence ratio of 1.0. Components of the thermally cracked n-decane at 3.0 and 5.0 MPa in a flow reactor were calculated theoretically using an accurately combined mechanism, which are in good agreement with the experimental results in literature. The results showed the conversion rates of n-decane cracking at 3 and 5 MPa are 46.2% and 58.8%, respectively. The distribution of cracking products is consistent, but the ethylene content decreases with the increase of pressure, while the alkane content increases with the increase of pressure. Meanwhile, the content of free radicals at 3 MPa is slightly higher than that at 5 MPa, but the content of free radicals is very low. Ignition delay time increases with the decreasing of n-decane conversion and pyrolysis pressure, while higher ignition pressure can shorten it significantly. Furthermore, the presence of free radicals in cracked n-decane could accelerate the ignition process with ignition delay time shortening more than 15% when the conversion was less than 40%, compared with that of cracked n-decane without radicals.