Dihedral corner effect is an important characteristic of SAR images, especially for the strong scatters generated by buildings and other human-made objects. Changing the opening angle of the dihedrals is a popular method to reduce radar cross section(RCS). Bistatic radar, which has flexible geometric configuration, is a good way to detect stealth targets. This paper analyzes the bistatic scattering characteristic of different dihedral corner reflectors using geometrical optics methods. As for the multiple scattering effect in the dihedral corners, the general term formula is given to describe the multiple scattering times and echo angles. Besides, the RCS calculation formula of dihedral corner is extended to bistatic condition. Both theory and simulation results show that bistatic radar has the ability to detect changed dihedral corners and its bistatic SAR image formation is a strong point at the corner point under a certain bistatic angle.