In the present study, we investigated the effects of the different traffic on the driver’s situation awareness and the mental workload (MWL). The task used in this study was a medium fidelity, 3-dimensional simulation of a driving environment. The simulation required participants to drive the user’s car and perform a real-world driving task. After the simulated driving, participants were asked to complete two tests which assessed their situation awareness (SA). The mental workload measures in this study consisted of the physiological measures and the subjective assessment. Every participant performed two different traffic simulated driving conditions, one was low traffic, the other was high traffic. The results showed that with the increasing of traffic, the driving performance did not worsen, however participant’s mental workload increased, at the same time, the participant’s situation awareness performance deteriorated.Meanwhile, our results also demonstrated that recall-based SA test and recognition-based test was heterogeneous.