This study starts off from the fact that William Wordsworth meticulously and realistically describes what he has experienced in London. And then it elaborates upon the next step that his descriptive and literary strategies to reflect what he has seen into his mind are closely related to such poetic principles as he shows in the preface to Lyrical Ballads. This study asserts that the Prelude, as a reflection of his inmost nature, demonstrates his operations of mind and is an example to show his attempts to contrast and integrate what he witnesses, according to his own poetic principles, which has been left and represented as just images in his mind. It is evident that imagination is not just a maker of simple images in memory. Besides its capacity to create and coordinate them and its operations of the mind of the poet, it also should endow him with his self-reflective cognition and internal ties which could bind the perishable images. He can perceive similitude in dissimilitude and vice versa. This study demonstrates that the comprehensive structure of the Prelude is built on Wordsworth`s imaginative power of apposition and opposition. His efforts to depict what he sees as an external reality can be summarized into an expression, “Spots of time”. Even though they are discrete and discontinuous, his mind`s eye can read out their interrelations. What this study stresses out is to verify how Wordsworth discriminates, integrates, values and judges the imaginative forms of representation in his mind.