中文摘要：

对于经济周期波动现象出现的原因，各个经济学流派从不同角度进行了阐释。本文阐述经济周期波动理论研究的演进，分析各个流派理论的产生背景、主要结论和缺陷。对经济周期波动本质原因的研究有益于对我国市场经济体制下经济周期波动的理解，促进我国经济平稳和谐地发展。

英文摘要：

Various economic schools have given their reasons why business cycles appear from many aspects, which include inner and outer causes, aggregate supply and demand etc. This paper describes the evolution of the studies on the business cycles theories and analyses their backgrounds, main conclusions and pitfalls. Study on the causes of business cycles will benefit the understanding for China＇s business cycles under the market economy system, and promote China＇s economy to develop steadily and harmoniously.