Rheological properties of four different bitumen binders and their short term aged samples were tested under various testing gaps using dynamic shear rheometer（DSR）. Complex modulus master curves were built based on the CAM model in order to analyze the rheological differences when the gap changed. Black diagrams were applied to demonstrate the effects of film thickness on the rheological properties of binders， with the affecting factors discussed. In addition， film thickness index B was proposed to describe the film thicknesses sensitivity of binder rheological property for the quantitative analysis. The results indicate that， with the decrease of film thickness， complex modulus shows a decline trend for all binders tested. However， it was observed that a simple linear relationship cannot be used to depict these trends. A relationship between rheological properties and film thicknesses following the double logarithmically linear rule is established and B can be well fitted on the base bitumen binder. On the other hand， the molecular structure will be changed by modification and aging to a certain degree which may reduce the applicability of B.