Modern medical diagnose has higher demand for image archiving and communication, the medical image display technology is mainly studied under the Windows platform. According to the analysis of the DICOM 3.0 standards and file formats, the general idea of the conversion from DICOM format to BMP format is proposed. Based on the object-oriented programming idea, a format conversion class called CDicomConvert is designed by using Visual C++. The class encapsulates many data and methods for DICOM image processing, and the class CDib is also improved. The result of the software running shows that it can convert the DICOM file to BMP format, and the medical image can be displayed under Windows.