Ranhou ‘then’ is traditionally defined as a conjunction, indicating succession of two events. Adopting the methodology of Interactional Linguistics, this study explores semantic relations of ranhou in Mandarin face-to-face and telephone conversations. An examination of the data shows that besides succession, ranhou can express other nine semantic relations, including causality, progression relation, coordinating relation, adversative relation, additive relation, enumeration, hypothesis, alternative relation, concession and be no practical meaning as well. Meanwhile, prosodic features of ranhou are explored with the help of software Praat and Audacity. It is suggested that eleven semantic relations vary in mean pitch range and mean length. Although each token of ranhou differs from each other in prosody, with respect to loudness, ranhou can be stressed on ran, or hou and also be articulated without loudness. But in a whole, loudness of ranhou is mostly put on hou.