In this paper we propose a new approach(named "diamond model approach") for analyzing a business model from(A) three levels:(1) business object,(2) business process, and(3) business performance,(B) five modules:product, stakeholder, resources integration ability, return and risk, and(C) three flows:logistics flow, cash flow, and risk flow. Through comparing it with some classic approaches for studying business models, we show this diamond model approach of business models inherits advantages of those approaches, but much more comprehensive and systematic, and particularly good at studying business models of the financial industry, which concerns about risk characters. A case study of online Ping An financial mall is made with the diamond model approach and some management insights are presented.