A data warehouse is an information provider that collects necessary data from individual source databases to support the analytical processing of decision -support functions. In the past, research on data warehouses primarily focused on relational data models. In this paper, the concept of object -oriented data warehousing is introduced, and three algorithms, including instance-insertion, instance-deletion and instance-modification, are proposed to maintain the consistency between the data warehouse and the source databases. Time complexity is also an alyzed to show their performance.