Abstract: Scientific theories are the central problem of the research of philosophy of science,which play a key role in the research of scientific explanation,theoretical evaluation and other issues.In the early stage of scientific theory,Hempel's conception of scientific theory was standing on the point of view of logical empiricism and insisted on the “Standard Conception” of scientific theories.Later,he gave up the idea of “Standard Conception” of scientific theory,and finally put forward the reticular structure model of scientific theory,which includes internal principle and bridge principle.His scientific theory has three natural characteristics : first,scientific conception is the foundation of the formation of scientific theory;second,theoretical entity has very important status in scientific theory;third,explanation and understanding are the main function of scientific theory.Moreover,Hempel's thoughts of scientific theory inevitably has some theoretical defects.

Key words: Hempel, scientific theory, logical empiricism, the reticular structure model