A lung simulator utilizing flow track to simulate spontaneous breathing is presented as an alternative to the existed lung system in the medical patient simulator. The hardware of simulator is similar and updated from Meka’s paper. The existing lung system can be divided into two main types. One is traditional bellows driven mechanical lung system, the other is bellow-less lung simulator driven by carinal pressure that to be controlled. Our lung simulator is upgraded from bellow-less simulator. The research focus on the flow pattern the lung simulator generated which can image the lung mechanical factors directly. The flow pattern of the lung simulator is modeled by transfer function combined with respiratory muscle pressure, which is the target that the bellow-less lung simulator to track. The target flow pattern is tracked by PID algorithm widely used in automation filed and realized by Control Design and Simulation module in LabVIEW. We simulate the normal respiratory motion by flow track in this study. The pathology breath flow can be simulated by change of resistance, compliance or muscle pressure, which is easy to adjust in the LabVIEW program.