In this scientific research, MnO2 nanoparticles (NPs) have been successfully prepared by a precipitation method using KMnO4, MnSO4.H2O and H2O2 (30%) as the precursors. As-prepared sample was identified by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Infrared (IR) techniques. The transmission electron microscopy (TEM) showed 7-8 nm ranges size of as prepared MnO2 nanoparticles. The decontamination reaction of triethyl phosphate (TEP) as a chemical warfare nerve agent simulant (CWNAS) was carried out on the surface of MnO2 NPs as the sorbent catalyst with the different weight ratios of TEP/MnO2 (1:8, 1:16 and 1:32) and studied by using phosphorous-31 nuclear magnetic resonance spectroscopy (31PNMR) technique. The 31PNMR analysis results proved that more than 95% of TEP was adsorbed on this catalyst in decane solvent with ratio of 1:32 after the elapse of the reaction time (8 h) at room temperature (25±1°C). On the other hand, decontaminated agent simulant amounts for the ratios of 1:16 and 1:8 were lower under similar conditions, respectively. This sorbent catalyst provides enough surface area and enhanced chemical reactivity for instantaneous adsorption and decontamination of TEP.