In the process of organic fertilizer machine composting, there are many factors that affect the fermentation of manure and other organic wastes, including carbon to nitrogen ratio, moisture, particle size and pH. This article mainly explains the influence of pH on fecal fermentation and organic waste fermentation. Unsuitable pH affects the reproduction, decomposition and survival of fermenting bacteria. Although scholars in the biological research field have certain differences on the appropriate absolute value of pH for fecal fermentation, they all agree that fermenting bacteria are suitable for growth in a neutral or alkaline environment. The neutral or alkaline environment is conducive to the reproduction and decomposition of fermenting bacteria. And survive.