Abstract：With the rapid development of economy, commercial advertisements have became an important part in people's social life. Commercial advertisements attract the attention of a growing number of experts and scholars. They analyze and study commercial advertisements from different perspectives. However, just few of such experts and scholars have been applying the Principle of Least Effort during this process. Some advertisements themselves demonstrate most simplified languages. They reflect the Least Effort in language. This thesis aims at studying the functions of the Principle of Least Effort in commercial advertisements, such as the functions of simplification, ellipsis, rhetoric and so on. The whole paper is made up of five chapters. Chapter one presents a brief introduction. Chapter two is literature review of the development of the Principle of Least Effort. Chapter three explores the feasibility of this principle in commercial advertisements. Chapter four is the main part of this paper, illustrating and analyzing the functions of this principle in commercial advertisements. Chapter five is the conclusion.
Key Words: the Principle of Least Effort; commercial advertisements; simplification; ellipsis; rhetoric

摘  要：随着经济的发展，商业广告已成为人们生活中重要组成部分。它吸引了越来越多的专家学者的注意。他们从各个方面研究商业广告，但通过省力原则研究商业广告的还不是很多。一些广告本身就是一种最简化的语言，它本身就体现了语言的省力性。本文主要研究省力原则在商业广告中的一些功能运用，例如简化功能，省略功能，修辞功能等。本文分为五个部分，第一部分是绪论；第二部分总结了省力原则的国内外研究现状；第三部分介绍了省力原则在商业广告中的可行性；第四部分是本文的主要部分，分析说明了省力原则在商业广告中的功能；最后一部分是本文的结尾。
关键词：省力原则；商业广告；可行性； 简化； 省略；修辞

Advertisements play an important role in the modern economic and social life and have become the indispensable part. It has been widely accepted by people recently. Now in the era of economic globalization, advertisements exist everywhere. Due to the importance of the advertisement, it attracts the great attention of experts and scholars.
Advertising language is the soul of an advertisement. With the rapid development of the modern advertising industry, advertising language has been integrated into our daily life. It is a new form of the existing language, and can even be viewed as a very active field of the usage of language. As a research area, it can further enrich our understanding of language. One principle that must be abided by when studying the advertising language, is the Principle of Least Effort. It is also addressed as "the principle of economy".