Purpose: The rock magpie (copshycus malabarichus) is one type of songbird that is the favorite of the contest. The average life span of the magpie batu is up to 15 years with a size ranging from 15-25 cm. Therefore, the need for information is very important for ordinary people to overcome problems regarding magpie bird diseases which can only be resolved with the help of experts. This disease can be caused by a virus or bacteria attack, to diagnose the disease you need visible symptoms. Based on this, researchers want to build an expert system that can be used to diagnose diseases in the rock magpie bird (copshycus malabarichus) based on selecting symptoms to find out the treatment for the disease. The expert system that will be built uses the Case Based Reasoning (CBR) algorithm which will be implemented on a website Findings/result: Case Based Reasoning makes decisions for new cases based on solutions to past cases that have occurred. The results of testing the Case Based Reasoning (CBR) algorithm produced a diagnosis of disease in the magpie batu bird (copshycus malabarichus) with a level of similarity to a disease of 83.3%, so this method can be used to diagnose the disease of the magpie stone bird (copshycus malabarichus) thereby helping ordinary people to diagnose diseases in magpie batu birds and treat them immediately before it is too late.