In this paper, a load-based joint call admission control (LJCAC) scheme for heterogeneous wireless networks is proposed. The LJCAC scheme aims to achieving the load balance in heterogeneous networks as well as guaranteeing the quality of service (QoS) satisfaction. We also develop the analytical models to calculate the connection-level performance of the proposed LJCAC scheme in two typical heterogeneous scenarios which are with overlapping and isolated coverage. The blocking probability of originating calls and dropping probability of vertical handoff requests are respectively evaluated. The results demonstrate that substantial performance improvement can be achieved by applying the proposed LJCAC scheme. The analytical and simulation results show good agreement.