The future satellite communications system is required to support the higher transmission data rate for providing the multimedia services by employing the efficient modulation method such as multi-level QAM. However, the employment of multi-level QAAM in the satellite channel would cause the fatal degradation of signal quality due to the non-linear amplifiers located at the earth station and satellite. To overcome this problem, we have proposed the multi-level QAM-OFDM technique with IDAR (Improved Decision Aided Reconstruction) method. In the IDAR method, the characteristic of non-linear amplifier is required as the known data at the receiver for mitigating the inter-modulation noise. This paper proposes the estimation method for AM-AM and AM-PM characteristics of non-linear amplifier by using the low PAPR (Peak to Averaged Power Ratio) preamble symbols. This paper presents various computer simulation results to verify the effectiveness of proposed method in the non-linear satellite channel.