This paper presents an analytical method to design proportional integral controllers for the stability, performance and robustness of third order plus time delay system models. Controller design is focused on providing desired gain and phase specifications of the controlled system by considering the frequency responses of an ideal system. Equations that give the parameters of the proportional integral controller which satisfy the mentioned properties are built step by step. These include the generalized equations for such systems. With the help of this method, the researcher can provide desired gain crossover frequency and the phase margin for third order plus time delay systems. Therefore, the Bode diagram can be relatively tuned and system performance and robustness can be improved. At the same time, stability of the system can be achieved with the proposed equations. Proposed controller parameters in this paper are applied on two different models. All results are shown graphically and on tables.