The destruction of methylphosphonic acid (MPA), a final product by hydrolysis/neutralization of organophosphorus agents such as satin and VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothionate), was investigated in a a bench-scale, continuous concentric vertical double wall reactor under supercritical water oxidation condition. The experiments were conducted at a temperature range of 450-600°C and a fixed pressure of 25 MPa. Hydrogen peroxide was used as an oxidant. The destruction efficiency (DE) was monitored by analyzing total organic carbon (TOC) and MPA concentrations using ion chromatography on the liquid effluent samples.The results showed that the DE of MPA up to 99.999% was achieved at a reaction temperature of 600°C, oxygen concentration of 113% storichiometric requirement, and reactor residence time of 8 sec. On the basis of the data derived from experiments, a global kinetic rate equation for the DE of MPA and DE of TOC were developed by nonlinear regression analysis. The model predictions agreed well with the experimental data.