Abstract: In discretely connected precast RC floor/diaphragms (DCNPD), slab joints are connected by connectors to transfer internal force. An analysis program of internal force and deflection under vertical load was conducted to accureately determine the vertical strength of DCNPDs. The moment and deflection eqations of a DCNPD simply supported on four sides under uniformly distributed load are derived according to the small deflection theory of elastic thin perpendicular heterogeneous plates and are solved with trigonometric series. A model for estimating the bending stiffness of a DCNPD in the transverse direction is proposed and validated by comparing with finite element solutions and experimental results. The moment and deflection distributions of a DCNPD are ideally spatial parabolical, indicating that the DCNPD has excellent bidirectional mechanical behavior. The moment can be effectively transferred by the slab joints, especially in the slab laying direction rather than the orthogonal direction.