The controllability of mining is a key factor affecting the commercial application of methane hydrates, and the addition of chemical additives can significantly accelerate the mining process. However, the effect of additive concentration on hydrate decomposition is not yet well understood. In this study, we systematically investigate the effect of ethanol concentration on the decomposition of methane hydrate under varying thermodynamic conditions using molecular dynamics (MD) simulations. To quantitatively characterize the decomposition process and mechanism of methane hydrates, the combination of angular order parameter (AOP), radial distribution function (RDF), mean square displacement (MSD), diffusion coefficients and system energy was for the first time used. The results showed that the addition of ethanol contributed to the formation of methane bubbles and accelerated the decomposition of hydrates. The mass transfer effect of ethanol molecules and the reconstruction of the hydrogen bond network of water molecules determined the stability of hydrates. From 0 to 40 mol% ethanol concentration, the hydrate decomposition increased with increasing the concentration of ethanol. Both increasing the temperature and decreasing the pressure are beneficial to the decomposition of the hydrate system. These results provide the selection of optimal ethanol concentration for the decomposition of methane hydrate and reveal its decomposition mechanism, and shed important light for the controllable production of gas hydrates.