Abstract: In order to increase the information security in information transmission，A communication technique based on information entropy and chaotic coding is proposed for modulation encryption． Theoretically，this technique chooses modulation methods adaptively for the signal with low bit error rate in accordance with realtime SNＲ ( Signal-Noise-Ｒatio ) estimation． It also increases the information security performance of the modulated signal by switching one modulation method to another according to the chaotic cipher codes．Numerically，an experimental implementation using time-variant channel，7 modulation methods and the chaotic Logistic map，demonstrates the validity and effectiveness of this technique．

Key words: information entropy, chaotic coding, modulation-hopping technique, chaos, signal-noise-ratio( SNＲ) estimation