A series of ReaxFF-MD simulations are employed to illuminate the oxidation mechanism of HFO-1336mzz(Z) as an environmentally friendly refrigerant in O-2/H2O environment. The results showed that H2O molecule has a significant impact on the HFO-1336mzz(Z) oxidation reactions and promotes the rate of HFO-1336mzz(Z) oxidation decomposition. H2O molecule can react with H and O radicals to form OH radical and will provide more H atoms to combine with F radicals to generate HF molecule. The OH radical plays a crucial role in the HFO-1336mzz(Z) oxidation reactions because the reactivity of OH radical. CO2, COF2 and HF are dominant products and the other radicals COF, O, F, CF3 and CO2F have a significant impact on the HFO-1336mzz(Z) oxidation reactions. The chemical equations of HFO-1336mzz(Z) oxidation in different conditions are presented to expound the comprehensive oxidation mechanism. (C) 2019 Elsevier Ltd. All rights reserved.