Material development is important for training beginner student interpreters, as it guides the direction of interpreting learning. One key principle is difficulty progression, which requires a good knowledge of the indicators of difficulty. Since text structure outweighs words and sentences in the information processing of consecutive interpreting, this study argued that text structure should be introduced as one of the major parameters for scaling material difficulty. Therefore, it set out to explore how the text structure of source materials contributes to the difficulty of consecutive interpreting for beginner student interpreters. Text structure is specified as causal relations and additive relations at the microstructure and macrostructure levels. Experiment data revealed that at the microstructure level, additive relations were more difficult to process than causal relations, while at the macrostructure level, causal relations were more difficult to process than additive relations. The reasons for this could be the different features of these two types of rhetorical relations and the processing mechanisms they trigger in comprehension and memory. The results are expected to provide a reference for instructors in selecting and adapting materials for pedagogical purposes in the initial stages of consecutive interpreter training.