In this paper, an admission control algorithm called CDPF (call dropping proportional fairness) is proposed to realize the proportional fairness of call loss probability. It dynamically computes the admission threshold for each class call to control the accepted call number according to the average call arrival rate, the average call duration time and the average cell dwell duration time of each class, and thus guarantees the call loss probability proportion of each class. In CDPF, the call loss probability of each class changes with the network load, while their proportion keeps unchanged. Simulation results show that with the change of network load, CDPF guarantees the proportional fairness of call loss probability. Compared with the existing algorithms, CDPF has lower time complexity.