The rise of a literature genre can be ascribed to both the conflicts of the interior literary elements, and the composition of forces of the exterior elements such as politics, religion, science and culture of a certain age. Take the sonnet as an example, the Queen Elizabeth’s favor and promotion, together with the experimentation of rhymes and metrics by such poets as Wyatt, Sidney, and Spenser, is of vital importance for its prevalence, which is eventually consummated by Shakespeare. By examining the origin and variation of the sonnet in English literature history, with a focus on the poetic license, this paper attempts to demonstrate that Shakespeare’s artistic achievement is mainly based on his poetic invention. As the privilege of the poets, the poetic license on the one hand indicates the poets’ endeavor to break away from the convention; on the other hand, it also reflects the conflict between the bondage of grammatical rules and the freedom to express the thoughts and feelings of human beings. With the dawn of scientific revolution in the 17 th century, the prose gradually substitutes the verse and becomes the mainstream of the literary genre, which can be regarded as the ultimate result of the above conflicts.