The change of the service demand is hard to be controlled for an enterprise. The customers have to line up when the service capability has been fulfilled. Therefore, to increase the service rate in the quick service industry is the best way to keep the enterprise’s competitiveness. To serve customers directly is the major job of the forefront attendants; whenever lots of customer waits for service, attendants’ working pressure would be changed, and the pressure will influence the service rate of service from the attendants. The queuing system under pressure condition is always discussed with infinite queuing capacity as well as service rate, but it obviously conflicts with the truth. Based on the above-mentioned reason, this paper tries to construct a service function with upper limit of service rate, and then applying the “System Dynamic” model to conduct the simulation. In addition, the relationship between the changes of the ‘Pressure coefficient’ and the “working efficiency” would be discussed.