Abstract: To solve the problem of high false alarm rate for the preamble detection of Mode S 1090MHz Extended Squitter (1090ES) with low signal to noise ratio (SNR), a Constant False Alarm Rate (CFAR) preamble detection method based on multi-pulse matching filtering is proposed. Because the detection threshold is determined with the samples received during the low level of preamble, the proposed method has a certain suppression ability against false preamble in 1090ES data block. Simulation results show that, under lower SNR, the method proposed in this paper has better detection performance than the classification methods for detecting the 1090ES preamble, and can suppress the false preamble in data block of 1090ES well. Furthermore, the data processing load of subsequent equipment is reduced.