An Acousticmagnetic EAS system based on ARM CortexM3 is designed owing to bad antijamming ability, detection sensitivity, low detection range and high rate of false positives faults in common EAS system.This paper introduces the working principle and hardware structure diagram of acousticmagnetic EAS system, analyses the acousticmagnetic tags signal in time domain and frequency domain characteristics, proposes FFT spectrum analysis, signal crosscorrelation, calculate the least squares fitting line slope variance calculation, calculation of signal peak value and peak varieties of acousticmagnetic tags signal algorithm, and describes the system software design of the algorithm in detail.The practice test proves that the system has strong antijamming performance, high detection sensitivity, wide detection range, low rate of false positives, etc.