The paper analyzes traction substationpsilas structure and spare parts, product main model. It mainly studies the application of case-based reasoning (CBR) in the design of traction substation. The application adopts architecture and object-oriented presentation to represent productpsilas structure and case base. It adopts level-2 indexing to determine searching indexing and standardizes original data to make it suitable for systempsilas similarity calculation. It chooses corresponding similarity model calculation based on data type. It adopts case similarity calculation model with partial and whole similarity integrated and level-2 indexing based on database indexing and nearest algorithm.