中文摘要：

NLCG（Nonlinear conjugate gradients algorithm）算法广泛应用于音频大地电磁法（AMT）二维反演中,并且取得了良好效果。本文介绍了NLCG方法的基本理论,并应用该方法对不同的反演模式和不同的背景电阻率所得的反演结果分别进行对比,结果表明：二维NLCG反演方法TE和TM模式联合反演效果比单个TE、TM模式较好;选择异常体所在层围岩的电阻率作为背景电阻率是最佳选择。

英文摘要：

Nonlinear conjugate gradients algorithm（NLCG） is a widespread and effective method of audio-frequency magnetotelluric（AMT） 2D inversion in practice.The basic theory of NLCG applied to AMT has been simply described.According to the results of TE mode inversion and TM mode inversion,and inversion results of different background resistivity,it is found that TE and TM combined mode inversion has a much better result than TE mode inversion and TM mode inversions and the best choice is to choose the surrounding rock resistivity of anomaly body as background resistivity.