To fulfill the explosive growth of mobile communication traffic demands, the heterogeneous networks (HetNets) in which macro cells and small cells (picocells, femtocells) are coexistent have been widely discussed in LTE systems. However, with the increase of small cells, user equipments (UEs) will experience frequent handovers which not only induce high signaling overhead, but also raise the risk of call-dropping. In addition, the different cell coverages and irregular mobile traffic lead to unbalanced loading in the HetNets. An overloaded cell will suffer from high call-block-rate (CBR) and call-drop-rate (CDR), especially in mobility networks. This work addresses on these problems and proposes a novel handover process to adaptively adjust cell-individual-offset (CIO) based on different average cell loading. Moreover, an access control mechanism is also presented to resolve the resource shortage problem in a congested network. Simulation results show the proposed work can significantly improve CDR compared with previous works.