Device-to-Device (D2D) communications is regarded as an option to extricate cellular Base Stations (BSs) from heavy traffic load. With more devices using D2D communications, there is an urgent demand for more spectrum bands for D2D communications. To provide more licensed bands for D2D communications, downlink spectrum reuse is a promising way to solve this problem. In an FDD-OFDMA LTE network, discontinuous resource blocks (RBs) of downlink spectrum are allocated to the same cellular user, thus resulting in complex interference between D2D users and cellular users. In order to increase the number of D2D users in the system and to increase the capacity of D2D users, allowing RBs reuse by more D2D pairs is an effective method, which, however, may cause more complicated interference. Multiple D2D users communicate with the same RBs poses a trade-off between transmission power and D2D users data rates.To provide a high capacity and to serve more users, we propose the RICE algorithm to allocate continuous RBs to D2D pairs, by facilitating different D2D pairs to share the same RBs. Simulations show that the RICE algorithm provides the highest capacity as compared to the exclusive spectrum allocation (ESA) strategy and adaptive subcarrier allocation (ASA) algorithm.