The mismatch between electrical transmission properties and light absorption properties is one of the main reasons that limit the power conversion efficiency of organic solar cells. This contradiction could be efficiently resolved by light trapping structures which manipulate incident light and enhance light absorption. These structures essentially extend the photoactive layer thickness, therefore achieve light absorption equivalent to that of a much thicker layer, and nevertheless retain good charge transport properties of a thin layer. The characteristics and principles of these architectures such as plasmonics and photonic crystal are discussed in detail. The prospect of light trapping architectures is also presented. It may be helpful to expand the design ideas of organic solar cells and understand the advanced light management of the next-generation solar cells.