Quality by Design (QbD) is one of the most powerful strategies which act as a part of modern approach to pharmaceutical industry. The quality in the process and product is neither assures just by inspection nor testing the products, the quality should be built in by design. QbD is the concept of continuous gaining of relevant knowledge based on scientific principles and the information gained from pharmaceutical development and manufacturing experiences which implement into designing quality product. The purpose of this article is to discuss the various types of models that can easily use in QbD paradigm. These models can be applied at any stage of the QbD; hence it is necessary to have knowledge of various models. In present paper the various types of models, their developing strategies, importance and impact on the pharmaceutical quality is discussed. The applications of the models presented in this article are in accordance with the principles of ICH Q8, Q9 and Q10 guidelines.