The Call of the Wild is one of the masterpieces of the great American writer Jack London. The plot concerns a previously domesticated and even somewhat pampered dog named Buck, whose primordial instincts return after a series of events finds him serving as a sled dog in the treacherous, frigid Yukon during the days of the 19th century Klondike Gold Rushes. Principles of survival are frequently illustrated in The Call of Wild. Jack London, who was regarded as one of the greatest naturalist novelists in late 19th and early 20th century, expressed his philosophy of naturalism in The Call of the Wild. This thesis attempts to explore Darwin’s theory of “the big fish eat up the small, the fittest survive.” in The Call of the Wild by analyzing the writing background, the characterization of Buck’s attitude and London’s philosophy of naturalism, and to find out the influence of adaptation of the principles and methods of natural science, especially Darwinian view of natural on London and the hardship of his life. The thesis is presented by four chapters. First chapter introduces the writer and his literature, the theory of Darwin and naturalism; the first part of second chapter focuses on exploring “Survival of the fittest” by analyzing the writing background; the second part of it focuses on analyzing the changing of Buck- after Judge Miller's gardener's assistant, Manuel, abducts the dog and sells him to a trainer of sled dogs, Buck is forced to survive and adapt to conditions in Alaska and the Yukon and becomes the leader of the sled team after defeating Spitz in a battle. Finally Buck returns to the wild and becomes the alpha male of a wolf pack he met a few days after the death of Thornton - to reflect “Survival of the fittest”; the third part analyzes London’s philosophy of naturalism; the third chapter aims at an exploration of influence of principles of survival on London; and the last chapter summarizes the whole thesis.