The Software Defined Network (SDN) architecture, which is defined by Open Networking Foundation (ONF), can provide flexible bandwidth management for time-vary requirements to enhance the efficiency of resource utilization. The basic concept of SDN is to separate the control plane and data plane. By the tightly and centralized control, SDN can not only provide effective network security management, but also dynamically adjust the network resource according to the requirement to maximize the system throughput. In this paper, the proposed method adapts the SDN approach to improve the cellular network throughput. Both of Average Allocation (AA) and Focus Allocation (FA) methods are proposed to reallocate Resource Block (RB) under the avoidance of subcarrier interference for hot spot cells. Two cases with frequency reuse factor 1/7 and 1/12 were adopted to examine the efficiency of the proposed methods. The performance impacts of different numbers of hotspot cells with unbalanced traffic load scenarios were examined through simulations. The simulation results illustrate that both methods can improve the system throughput in above scenarios. Furthermore, the AA method achieves better throughput of hotspot cells when compared with the FA method.