Abstract The concept of city design is often very uncertain and hard to defne because it involves a great deal of factors such as behaviors, mentality, and social hierarchy. Understanding the defnition of urban design helps to understand its mechanism. It can be divided into two categories. The frst kind of urban design is the guideline to control and guide the urban form. Another kind of urban design is to integrate the existing urban environment through large scale project, and it can guide future development in this area. It could be called "guiding" and "feasible" urban design. What are the pros and cons of both approaches? A feasible urban design is more likely to have a positive impact in a direct and effective way. A guiding urban design works much better in the long term. Further, as a variable concept, urban design will constantly change, integrate with other disciplines and even fade away with the development of science.