In this paper, we present an interference-aware slot allocation technique to improve system performance of the hierarchical picocell/macrocell system, where low-power picocells are underlying a high-power macrocell. Although a hierarchical picocell/macrocell system can improve capacity, it also poses a challenging inter-cell interference (ICI) issue. To control the ICI between pico-cells and macro-cells, one enhanced inter-cell interference coordination (eICIC) technique, called almost blank subframes (ABS), was proposed in the 3rd Generation Partnership Project (3GPP) Long-Term Evolution-Advanced (LTE-A) system. Nevertheless, the current ABS mechanism in 3GPP only defines the fixed ABS ratio, which is not very spectrum efficient and can affect the macrocellular system performance. In this paper, we propose an interference-aware ABS ratio adaptation technique to enhance the total spectrum efficiency of the hierarchical picocell/macrocell system. Compared with the current fixed ABS ratio approach, the proposed method can improve the spectral efficiency of pico-cells and macro-cells by 13% and 7% at the cell edge, respectively.