The target detection has drawn significant attention because of its wide applications. In this paper, the method of multiple observations adaptive matched filter (MOAMF) is proposed with aid of the GLR principle. The probability density function is analyzed, the test statistic is investigated and the analytical expression of the MOAMF is derived, then the false alarm and detection probability conditioned on observations size are given. The simulation shows high agreement with the proposed method and the analytic results validate the correctness of detection probability. To compared with the AMF with different observations, the MOAMF outperforms dramatically, especially when the observations is larger than 1.