The reaction pathways for the ClO + HOCO reaction have been explored using the coupled-cluster method to locate and optimize the critical points on the ground-state potential-energy surface. Results show that the ClO + HOCO reaction can produce Cl + HOC(O)O, HOCl + CO2, HCl + CO3, and HClO + CO2 via an addition or a direct hydrogen abstraction reaction mechanism. The reaction kinetics has been studied using the variational RRKM theory. It is found that the ClO + HOCO reaction is fast and has a negative temperature dependence at low temperatures. At room temperature, the thermal rate coefficient is obtained as 4.26 x 10(-12) cm(3) molecules(-1) s(-1) with product branching fractions of Cl (0.518), HOCl (0.469), HCl (0.01), and HClO (0.003) at zero pressure, The Cl + HOC(O)O products are major, compared to the HOCl + CO2 products, because of the loose transition state along the dissociation pathway to eliminate Cl. In addition, the RRKM/master equation simulations indicate that the stabilization of the HOC(O)OCl intermediates is noticeable at moderate pressures as its thermal rate constants reach about 6.0 x 10(-13) cm(3) molecules(-1) s(-1). In contrast, the other product branching ratios for the ClO + HOCO reaction are weakly dependent on pressure.