MD3DAF is an Object-Oriented and Component-based 3D Graphics Application Framework,aiming to simplify the development of 3D application such as CAD and GIS basing on Microsoft .Net frameworks and Managed Direct3d.It is written in C# and provides classes,interface and utility library that can be resued by programmer. MD3DAF will implement many import function of 3D graphics application for geoemetry arithmetic,drawing creating,drawing editing and so on.Programmer can develop graphics application or add graphics feature to their application by extending and cumstomzing MD3DAF.