Cooperative diversity is a new technology to improve bit error rate (BER) performance in wireless communications. A new power allocation algorithm to improve BER performance in cellular uplink has been proposed in this paper. Some existing power allocation schemes were proposed for the purpose of maximizing the channel capacity or minimizing the outage probability. Different from these schemes,the proposed algorithm aims at minimizing the BER of the systems under the constraint of total transmission power. Besides this characteristic,the proposed algorithm can realize a low complexity real-time power allocation according to the fluctuation of channels. Simulation results show that the proposed algorithm can decrease the BER performance of the systems effectively. Cooperative diversity is a new technology to improve bit error rate (BER) performance in wireless communications. A new power allocation algorithm to improve BER performance in cellular uplink has been proposed in this paper. Some existing power allocation schemes were proposed for the purpose of maximizingizing the channel capacity or minimizing the outage probability. Different from these schemes, the proposed algorithm aims at minimizing the BER of the systems under the constraint of total transmission power. Besides this characteristic, the proposed algorithm can realize a low complexity real-time power allocation according to the fluctuation of channels. Simulation results show that the proposed algorithm can decrease the BER performance of the systems effectively.