As a result of the significant increase of overlapped coverage areas among base stations (BSs), interference coordination in heterogeneous cellular networks (HetCNets) becomes necessary, since interference would degrade network performance and even cause dropped calls. In addition, various types of BSs coexist in HetCNets, and BSs with low power (such as Pico BSs and Femto BSs) are deployed more arbitrarily than those in macrocell BSs (MBSs) so that the traditional anti-interference technologies are not enough in HetCNets. To reduce the interference between MBSs and low-power BSs within the coverage, a novel distributed resource allocation algorithm is proposed. First, an interference graph is established, by which the corresponding orthogonal resources can be assigned to different BSs, and the users can be classified into center and edge users, respectively. After that, users select appropriate resource blocks according to an improved proportional fair algorithm, and BSs distribute transmission power to different resource blocks to enhance network throughput further. Simulation results demonstrate the effectiveness of our proposed scheme in resource allocation and utilization.