Process oscillation characterized by a long oscillation period and a large oscillation amplitude was observed in continuous ethanol fermentation with Saccharomycescerevisiae under very high gravity（VHG）conditions.Flow cytometry was used to determine the cell cycle distributions at different time points in the duration of the oscillation.Analysis for the yeast cell cycle indicated that no cell cycle-dependent synchronization happened within the duration of the oscillation.Metabolic flux analysis was carried out and the results illustrated that the carbon flux within the metabolic network oscillated correspondingly.Ethanol inhibition and the lag response of yeast cells to ethanol inhibition were experimentally validated to be the root reason triggering this phenomenon，which was further supported by the synchronized accumulation of the intracellular trehalose，a stress-resistant agent.