To improve the positioning accuracy of positioning systems, a time of arrival (TOA) estimation algorithm based on a preamble four-pulse signal differential matched filter is proposed. Using the two-pulse and four-pulse signals to evaluate the differential matched filter, the TOA estimation accuracy of preamble pulse signals is improved. Based on the number of pulses and a signal-to-noise ratio (SNR), the root mean square error of the differential matched filter output is compared, it is concluded that the TOA estimation accuracy of four-pulse signals is better than that of single-pulse signals. When the SNR is 20 dB, the TOA estimation accuracy of the four-pulse signals can reach 3.8947 ns, which is much lesser than the maximum time error accuracy of 25 ns specified by the International Civil Aviation Organization. Real-time data received by an ADS-B receiver installed at the terminal of Tianjin Airport and simulation data under the same conditions are used to verify the accuracy and stability of the TOA estimation of proposed algorithm.