Using a heated shock tube and an spectroscopic detector ICCD, transient emission spectra of n-heptane, n-decane, xylene and isooctanein the combustion reaction were measured in the range of ultraviolet to near infrared. Experiments were conducted at apressure of 1.5 atm and a temperature of 1500 K. Results show that the main emission bands are attributed to CH、OH and C₂ radicals produced during the combustion process, and the small radicals CH、OH and C₂ are the important reaction products in the combustion process of n-heptane, n-decane, xylene and isooctane; The results are consistent with the combustion kinetics mechanism; Determined the electron level transitions corresponding to the characteristic spectra of CH、OHand C₂ radicals. Analyzed the production mechanism of small free radicals of CH, OHand C₂from the perspective of chemical reaction with the theory of combustion kinetics. The results provide experimental basis for understanding the microscopic process of hydrocarbon fuels combustion reaction and verifying the mechanism of hydrocarbon fuels combustion reaction.