In this paper, the authors present the design and implementation of an Interoperable Object Platform for Multi-Databases (IOPMD). The aim of the system is to provide a uniform object view and a set of tools for object manipulation and query based on heterogeneous multiple data sources under client/server environment. The common object model is compatible with ODMG2.0 and OMGs CORBA, which provides main OO features such as OID, attribute, method, inheritance, reference, etc. Three types of interfaces, namely Vface, IOQL and C++ API, are given to provide the database programmer with tools and functionalities for application development. Nested transactions and compensating technology are adopted in transaction manager. In discussing some key implementation techniques, translation and mapping approaches from various schemata to a common object schema are proposed. Buffer management provides the data caching policy and consistency maintenance of cached data. Version management presents some operations based on the definitions in semantic version model, and introduces the implementation of the semantic version graph.