Methane hydrate decomposition was investigated by molecular dynamic simulation adding with polyvinyl alcohol. Three kinds of methane hydrate systems with polyvinyl alcohol concentration of 2.7 wt%, 5.2 wt%, 7.6 wt% respectively were studied. Water moleculars in methane hydrate fluctuate near the equilibrium position when polyvinyl alcohol (PVA) concentration is 2.7 wt%, with diffusion coefficient 1.04×10^－11 m²/s; while at 5.2 wt% PVA solution, methane hydrate structure was disrupted, most methane escaped from the cages, with diffusion coefficient of water molecular 1.61×10^－9 m²/s, showing good ability of hydrate decomposition. Hydrogen bond was observed between PVA itself, causing steric hindrance in hydrate formation. A small parts of methane hydrate cages at interface were disrupted, resulting some methane escaped, the diffusion coefficient of water molecular is 3.55×10^－10 m²/s in 7.6 wt% PVA solution. As for effect on decomposition of methane hydrate, PVA concentration 5.2 wt% is the greatest, while the PVA concentration 2.7 wt% is the least. This work provides great reference value for the experimental investigation into the effect of PVA on the hydrate dissociation.

Key words: polyvinyl alcohol, methane hydrate, molecular dynamic simulation, decomposition