Willa Cather(1873-1947)is one of the most famous American female writers.Her reputation as one of the finest novelists rested on her novels about AmericanMidwest prairie.O Pioneers!My Antonia and The song of the Lark are regarded asher trilogy of Nebraska Novels.In these novels Cather not only depicts theextraordinary beauty and spiritual grace of the prairie frontier but also sings a song forthe pioneers’persevering spirit. O Pioneers! is Cathers first mature Nebraska novel.It lays a solid foundation forher literary creation.Ever since its appearance，it has attracted many critics’attention.They interpreted it from different perspectives such as romanticism，nationalism,eco-feminism and so onAlongside these analyses some readers began to payattention to its transcendentalism recently. Being infused with transcendentalism from her childhood，Cather’S literarycreation Was influenced greatly by it.Transcendentalists deny the sovereignty of God，affirm the divinity of man，and advocate human’S self-reliance.They also denyhuman’S material enjoyment，affirm human’S spiritual pursuit，and advocate people tosink completely into nature for spiritual improvement and perfection.The ideas notonly permeate Cather’S meditation on mind，nature and life but also run through herlifetime literary creation. This thesis is intended to explore the transcendentalism embodied in O Pioneers!by the characterization.It mainly consists of three parts。Part One discusses Americantranscendentalism and its influence on Willa Cather’S literary creation.Part Twoexplores“nature as the symbol of spirit”by the characterization of Alexandra and Ivar.The two characters both show intuitive love for nature.They desire for sinking intonature to get their spiritual improvement and perfection.The characterization of themreveals Cathers consciousness，which coincides with the transcendentalists’idea：Nature is the symbol of spirit or the Oversoul.Part Three analyzes“self-reliance”embodied in the novel by the characterization of Alexandra BergsonAlexandra hasstrong confidence.She always keeps an optimistic outlook for her lifeAt the sametime, she is unconventional and always bravely challenging the prejudices againstwoman in a patriarchal society. She also focuses on self-cultivating for becomingmore perfect. All these are the good expression of her self-reliance. With strong senseof self-reliance she succeeds in cultivating the wild land to establish her femaleidentity in a prejudiced society, and overcoming her self-limitations to attain her idealmarriage。 Based on the above analysis we know that the transcendentalists thoughts suchas "self-reliance", "individualism" and "nature as the symbol of spirit" are fullyembodied in the novel。