In recent years, femtocells are receiving considerable attention towards increasing the network coverage, capacity, and improving the quality of service for users. However, as the femtocells use the same radio band, it poses a serious cross-tier interference issue. In this paper, a reasonable and effective interference suppression scheme, that is, quality of service based fractional power control (QoS-FPC) under the HetNet environment is proposed. The proposed scheme limits the cross-tier interference at eNB below a given threshold, and hence results in the optimization of femtocell users power allocation and system throughput.