The effect of temperature on the formation of C10H7O2 in the C10H7 + O2 reaction has been investigated at temperatures 299-444 K by directly monitoring the C10H7O2 radical in the visible region by cavity ringdown spectrometry (CRDS) using the 2-C10H7Br as a radical source photolyzing at 193 nm. The ?rst experimentally measured rate constant for the association reaction can be given by k1 ) (1.53 ( 0.10) ± 1012exp[(900 (45)/RT]cm3mol-1s-1, where R is gas constant and 1.986 cal/mol-K, at a total pressure of 40 Torr in the temperature range studied. Theoretically the association process was computed by B3LYP/6-31+G(d, p) with the energy pro?le improved at the G2MS level of theory. The excitation energies and oscillator strengths of the association product (2-C10H7OO) were calculated by using the time-dependent DFT method. The association rate constant of this reaction was predicted by the canonical VTST/RRKM theory with the steady-state and master-equation analyses. The latter method gave a much better agreement with the experimental data.