Software Product Line (SPL) is at the forefront among the techniques for reducing costs, decreasing schedule time, and ensuring commonality of features across a family of products - as components off-the-shelf (COTS) are reused in multiple products. A disciplined process for software product line development is still needed. We propose the Y-model for COTS-based software product line development. The model put forward identifies and elaborates the essential phases and activities of software product line development from COTS-based repository. The Y-model provides an efficient way of integrating the approaches of software product line and COTS-based development as a cohesive software development model. The model has the potential to tremendously increase software engineers' productivity. Thus software architects, domain engineers and component designers should become aware of how to use these ideas to structure their models and designs. The model has the potential to tremendously increase software engineers' productivity. Thus software architects, domain engineers and component designers should become aware of how to use these ideas to structure their models and designs.