Recently, with progressive development of science and technology, it is evident that efficient guidance algorithms is an integrated part of guided vehicles. In a guided vehicles, the control system or autopilot calculates the appropriate commands to the control surfaces and that signal is also applied to the vehicle actuators. The guidance system can be imagined as an outer loop which provides appropriate command signals to the control loop. Among the existing guidance algorithms, proportional navigation (PN) is the most widely used. In this way, the vehicle lateral acceleration commands are proportional to line-of-sight rate between the vehicle and target. The line-of-sight rate can be directly measured by an embedded seeker. Today, in the guided vehicles, guidance algorithms equipped with a seeker have been interested. A guidance loop based on seeker includes some subsystems like vehicle dynamics, the type of flight path and also navigation sensors which each of these subsystems may have some parameters. It is trivial that the guidance system performance would be affected by changing in these parameters. In this study, in a typical vehicle equipped with a seeker, we are going to investigate the performance and efficiency of guidance system in terms of the parameters changes. With such an approach, the parameters effect would be determined on the guidance system performance.