Power BI can connect to SSAS data in two modes: Import mode and DirectQuery mode. Import mode pulls all the data from SSAS into Power BI for local caching, but changes in SSAS won't be reflected automatically. DirectQuery mode sends queries directly to SSAS in real-time, allowing users to see changes immediately without refreshes, but it can impact performance for large or complex queries. The choice of mode depends on factors like data size, refresh needs, and query complexity.