PLC, or programmable logic controller, is a type of microprocessor-based digital computing controller. It can be used for automatic control, storing and executing control instructions loaded into memory at any moment. In the process of classroom learning, the author learned about PLC, and the device to implement PLC is PLD, that is, a programming logic device, whose letters represent proportional controller, integral controller, and differential controller. In the process of learning, people noticed that proportional control is relatively simple compared with integral and differential control, but it is the most frequently used and widely used, so the author can't help but have a strong interest in proportional control. Through research and search, the working principle and working characteristics of the PLC were found because it has high reliability, convenient programming, adaptable setup, full input/output functional modules, and quick processing speed, which are used by many modern precision instruments. In the process of research, it was found that it was the K value that affected the proportional control, and the simulation using the false data image found that the model curve formed under different K values was also very different. Therefore, the research topic of this paper is the transformation of different graphics caused by the change of proportional control K in the PLC. The plots obtained by different K values are different, and the advantages and disadvantages of proportional control can be found.