A novel kinetic method for determination of $HO_2^{cdot}/O_2^{{cdot}-}$ in ozone decomposition in water is described. In this study, potential interferences of $O_3$ and the hydroxyl radicals, $^{cdot}OH_{(O3)} $, are suppressed by $HSO_3;^-/SO_3;^{2-} $. $HO_2^{cdot}/O_2^{{cdot}-}$ formed in ozone decomposition reduces $Fe^{3+}$-EDTA into $Fe^{2+}$-EDTA and subsequently the well-known Fenton-like (FL) reaction of $H_2O_2$ and $Fe^{2+}$-EDTA produces the hydroxyl radicals, $OH_{(FL)}$. Benzoic acid (BA) scavenges $^{cdot}OH_{(FL)}$ to produce OHBA, which are analyzed by fluorescence detection ($lambda_{ex}$ = 320 nm and $lambda_{ex}$ = 400 nm). The concentration of $HO_2^{cdot}/O_2^{{cdot}-}$ in ozone decomposition has been determined by the novel kinetic method using the experimentally determined half-life ($t_{1/2}$). The steady-state concentration of $HO_2^{cdot}/O_2^{{cdot}-}$ is proportional to the $O_3$ concentration at a given pH. However, the steady-state concentration of $HO_2^{cdot}/O_2^{{cdot}-}$ in ozone decomposition is inversely proportional to pH values. This pH dependence is due to significant loss of $O_2;^{{cdot}-}$ by $O_3$ at higher pH conditions. The steady-state concentrations of $HO_2^{cdot}/O_2^{{cdot}-}$ are in the range of $2.49;({pm}0.10){ imes}10^{-9}$ M (pH = 4.17)$sim$ $3.01;({pm}0.07);{ imes};10^{-10} $M (pH = 7.59) at $[O_3]_o$ = 60 $mu$M.