Abstract: The original meaning of "jiayou(加油)" is "to add oil", and its extended meaning "to make further efforts" is often used on occasions to encourage somebody in modern Chinese, especially the ones to encourage athletes in sports. In the 1920s, "jiayou" was a slang used in the canteen of Tsinghua School, originally referring to adding sesame oil to pickles. Subsequently, it gradually became popular in sports in Tsinghua School, which was used to encourage athletes and produced the meaning of "making further efforts". Through the transformation from canteen slang to stadium cheering slogans and from oral language to written language, the new meaning of "jiayou" tends to be solidified, and spread to the whole country through inter-school competitions. From encouraging athletes to encouraging the public, its application is gradually not limited to sports. The reasons for the evolution of the meaning of "jiayou" mainly are two: the first is that the word "jiayou" has the conditions to have the extended meaning of "making further efforts", the second is the development of modern sports in China are provided for the demand of language development, and at the same time, Tsinghua School entertains a unique context for the semantic evolution of "jiayou".