So far, the lecturer had already taught 4 chapters and he strongly emphasized that the subject of process control has become increasingly important in recent years. Without process control system it would be impossible to operate modern plant safely and profitably while satisfying the product quality and environmental requirement. Thus, it is important for us as chemical engineers to have an understanding of both the theory and practice of process control. Throughout the learning of this course, I found that I am getting more and more miserable when it comes to chapter 3 and chapter 4. I felt that this subject is a tough subject because it requires us to master the ordinary differential equation skills beforehand and apply it into the theories. No matter how hard it is, I will try to understand it thoroughly. The luckiest thing is that we have got a patient and considerate lecturer. He was trying hard to find out the part that we do not understand and willing to explain to us.