Abstract: Discourse cohesion and coherence is an important concept in the field of discourse analysis. Being a new model of meaning analysis, Default Semantics provides a new explanation for cohesion and coherence. Based on principles of intentionality and primary intention, the manifestation of discourse cohesion and coherence is in different logical units (discourse, proposition and proposition composition), the correlation of discourse meaning (primary meaning and default meaning) and the projection from meaning to logic forms, its cognitive basis is the interactive experience between discourse producer and receiver, the model of foreground-background and the oneness of the human mind.