Psychology is the study of human behavior and mental processes. The expert system applied in psychology is about testing the interests and talents of elementary school students. Interest and talent are very important issues in education. Through tests of interests and talents, students can better know their potential, including their strengths and weaknesses, both in terms of academic and personality. Expert system designed to determine the interests and talents of elementary school students, preferably for students in grades IV, V, VI. Because the class students have entered the age of around 10-11 years, where at that age is the age of transition to the real world when the cognitive abilities of children develop to plan something. These children have different characteristics and uniqueness, such as the existence of an interest in concrete, practical daily life. In designing this expert system using a method that is Case-Based Reasoning that can predict and identify interests and talents according to the ability of these students.