Abstract: Aimed at the amplitude estimating problem for paired carrier multiple access (PCMA) signals, an amplitude estimating algorithm which combines the high square method and the cumulative cost function is proposed. The algorithm calculates the amplitude ratio of two signals by solving the minimum of cumulative cost function. The amplitude of the strong signal is estimated by four square method. And these two estimations are used to estimate the amplitude of the second signal. The influence of frequency difference and oversampling multiplier on the estimation performance is studied. Simulation results show that the algorithm has lower complexity and stronger noise resistance. Compared with the existing algorithms, this algorithm is not only suitable for symmetric PCMA signals which contain a twoway signal with a greater difference in amplitude, but also for asymmetric PCMA signals which contains two signals with less amplitude difference.