This paper suggests the product supply process model based on the store and production capacity, assortment planning and quick response for fast fashion retailers with BPMN. In the fast fashion industry, the standardized business process model is required to respond quickly market trends and customer requirements based on the quantitative and qualitative criteria. Thus we define the product supply processes which incorporate forecasting and assortment plan, cost and profitability of the production, store capacity based on the visual merchandising, and production capacity of the fast fashion retailers. Also we design the key performance indicators to evaluate the effectiveness of these product supply processes. The product supply process model for the fast fashion has great significance in embracing the fast fashion product development process because it presents the holistic view of the product supply process of the fast fashion and provides a performance evaluation mechanism. A case study shows that adopting the processes, a Korean fast fashion company achieves improvement in various performance indicators.