With development and impact of ICT, the method of work in many organizations has been becoming more collaborative and communicative, under which a number of organizations start to take corresponding strategies to achieve business goals and create more values. Managing Business Process is an effective and efficient way to improve productivity and performance of business activities from an organizational level. Business Process model, as a representation of Business Process, provides a big picture of Business Process, allowing organizations to acquire understanding on logical relationships among different business activities and to improve Business Process by various approaches. This study discusses the application of Business Process models on weakness identification which is related to the problem of excess inventory in supply chain with a qualitative method. It adopts three Business Process Modelling techniques to build Business Process models for a planning team involved with demand and supply planning, where four experts from the team participate in interview. The models are analyzed according to selected weakness patterns in order to identify the process weaknesses and link them with the causes of excess inventory. The result of this study gives a positive answer, which means the Business Process Models are capable to identify causes for the concrete problem of excess inventory by identifying process weaknesses.