Abstract: Traditional Soft Frequency Reuse (SFR) can not adapt to dynamic traffic distribution in Long Term Evolution (LTE) systems, leading to imbalanced spectral efficiency in cell center and edge area. In order to solve this problem, this paper proposes a Dynamic Spectrum Allocation scheme for LTE system by exploiting Cognitive capability (Cog-DSA). By exploiting inter base station cooperation, spectrum use status is acquired. Then the available spectrum set is determined and co-channel interference from adjacent cells is evaluated. Finally, dynamic spectrum borrowing and service base station selection are implemented. Simulation results demonstrate that the proposed Cog-DSA method can effectively improve the spectrum utilization, mitigate inter-cell interference and significantly raise cell edge users' transmission rate.