Internal contact angle is an important parameter for internal wettability characterization. However, due to the limitation of optical imaging, methods available for contact angle measurement are only suitable for transparent or open systems. For most of the practical situations that require contact angle measurement in opaque or enclosed systems, the traditional methods are not effective. Based upon the requirement, a method suitable for contact angle measurement in nontransparent systems is developed by employing MRI technology. In the Article, the method is demonstrated by measuring internal contact angles in opaque cylindrical tubes. It proves that the method also shows great feasibility in transparent situations and opaque capillary systems. By using the method, contact angle in opaque systems could be measured successfully, which is significant in understanding the wetting behaviors in nontransparent systems and calculating interfacial parameters in enclosed systems.