The experiment uses the PID controller to control the level of tank. In the first we draw the P&ID form the real level process control and convert it to block diagram. The block diagram helps us analyze how it work and find the transfer function of the level process control. We can calculate the transfer function from block diagram or we can calculate it by step the input to the system (level process control). We step input to 10% and observe the output. The graph between input and output can calculate the transfer function of the system. Then we use the data from the transfer function to select the controller. In this experiment we use PI controller because P controller make the system slow and the steady state error. PID controller suit for the slow process but level process is the fast process. If we use PID in the experiment the D term cannot controller the fast output and can cause the system run away. The PI controller suit for fast process because it can control the output and reduce the steady state error. Then we tuning the PI controller for smooth and fast as it can. The process is cascade control. The cascade control in this experiment has two loops include master and slave. The slave loop is faster than the master loop and the set point in the master loop is remote set point of salve loop. We tune the slave loop fist and set it to auto mode. Then we tune the master loop and set it to auto mode to. Now we can control the level process by tuning of PI controller.