Abstract: In the dimensions of Systemic Functional Grammar, the application of the ecological analytical framework of discourse is conducive to the interpretation of the eco-pattern and the ecosophy implied in the lines of Emily Dickinson's nature poem What Mystery Pervades a Well, as well as its significance to mankind. It is found that there are three types of transitivity process in this poem which mainly involve the relations of “human and nature”, “nature and nonhuman organism”. Nature in this poem is described mysterious and scary to humans. In addition, the image of nature constructed in the poem is highlighted by the exclamative clauses, and the words with different degrees of modality value are used to imply that nature is also unfathomable. Besides, there are two main participants functioning as theme: nonhuman organism and physical places. And the frequent use of reference is to personify “nature” and “the specific plants” as “her” and “he” respectively. All these mean that nature should be respected. Moreover, by singing high praise for “the grass” and “the sedge” which give no evidence of fear towards nature, the poet indicates that all human beings should follow the natural rules rather than infringe upon nature.