Cattle are livestock that are in great demand by the people of Indonesia, especially in Magetan Regency, many cattle are kept because of their many benefits. This cow disease is a problem for farmers, of the many diseases in cattle, there are 7 diseases that often occur in Magetan Regency (Indigesti, Diarrhea, Worms, Scabies, BEF, PMK, LSD). The lack of even distribution of veterinarians adds to the obstacles for breeders to obtain information on handling sick cows. Therefore, this system was created using the ESDLC (Expert System Development Life Cycle) development stages and the Naïve Bayes algorithm, in order to provide fast and accurate information to cattle breeders. After testing with 2 veterinarians from the Magetan Regency Livestock and Fisheries Office and 2 breeders in Magetan Regency, the results of the initial diagnosis and the data contained in the system matched the knowledge and experience of doctors and breeders, system and algorithm testing was also carried out. system testing using the white box shows the results of the system having a low level of risk for damage to occur. Algorithm testing uses Big-O notation which shows the results of O(1) Costant time, meaning that the Runtime is in line with the amount of data.