To study the regularity of driver workload in mountain city tunnel, the vehicle driving test on four mountainous city tunnels were carried out, and electrocardiogram(ECG) of driver, Velocity of vehicle as well as illuminance of tunnel under naturalistic urban traffic condition were collected. The heart rate growth (H) of driver affected by velocity and tunnel illuminance was analyzed based on the measured date. The relationship among the tunnel illuminance, vehicle velocity, and H was confirmed, and the regression model of these parameters was established. The results show that a strong negative correlation between tunnel light and H in the entrance section of tunnel, and with the increase of the velocity, H is more sensitive to the changes in the tunnel illuminance. There is a strong correlation between light and H, and a positive correlation between velocity and H exists in the exit section of tunnel.