Abstract: Beer fermentation is a crucial step in beer production, and temperature variation is a major factor. Therefore, controlling the fermentation temperature directly affects beer quality. This paper utilizes a PLC to control the temperature during beer fermentation, realizing a key technology. This system is simple in structure, low in cost, highly scalable and portable, and has practical application value. Keywords: Beer fermentation; Temperature control; PLC; Application Overview Beer fermentation is a process in which brewer's yeast participates in a series of metabolic processes on certain components of the wort, transforming the wort flavor into the beer flavor. Beer fermentation is a key step in the beer production process and an extremely complex biochemical exothermic reaction process that occurs and releases a large amount of heat within the fermentation tank. During this process, not only are enzymes in the yeast cells breaking down fermentable sugars and amino acids in the wort into ethanol and carbon dioxide, but a series of fermentation byproducts are also produced, such as diacetyl, higher alcohols, aldehydes, acids, and esters. Although the content of these metabolites is extremely small, they have a significant impact on beer quality and flavor, and the formation of these intermediate metabolites depends on the fermentation temperature. Therefore, the normality and smoothness of the fermentation process directly affect the quality of the final beer product. For example, drastic temperature changes during fermentation can cause premature sedimentation, aging, death, and autolysis of yeast, leading to abnormal fermentation. It also directly affects the composition of yeast metabolic byproducts, thus harming the beer's body, flavor, and colloidal stability. Therefore, controlling the fermentation process has always been highly valued by brewers. In the past, the control of various process parameters during beer fermentation was achieved using conventional tables, manual on-site adjustments, and manual recording. However, with the continuous increase in beer production and the growing number of fermentation tanks (some plants now have 30-40), continuing with conventional methods would not only cause significant inconvenience to workers due to the large number of instruments, but also lead to unstable production quality and even production accidents due to negligence, errors, and other human factors. Therefore, a programmable logic controller (PLC) was designed to automatically control the beer fermentation temperature. For details, please click: Application of PLC in Beer Fermentation Temperature Control.