The features of using noise resistant encoding for protection from errors in digital data transmission channels with phase modulation have been analyzed. The building principles and encoder and decoder schemes of turbo-code were observed. The digital data transmission system with outer and inner turbo-encoder has been developed. The recommendations to type and structure of cascade encoder components have been given. Analytical relationships and research results describing bit error probability of cascade turbo-encoder components are represented. By using simulative modeling tools Matlab-Simulink the basic characteristics and features of digital transmission channel with cascade turbo-encoding and digital phase modulation were researched. The energy benefit gained by using cascade structures has been defined.