In this study, the concentration levels of NO₂, O₃, and SO₂ at the crossroad of Haier Road and East Yinchuan Road, Qingdao, are continually monitored in real-time based on the long path differential optical absorption spectroscopy (LP-DOAS) from 2017 to 2018. The concentration levels of NO₂, O₃, and SO₂ obtained using LP-DOAS are compared with those obtained at the environmental monitor station, and a good agreement between these is found. The correlation coefficients of NO₂ and O₃ hourly average results are 0.78 and 0.798, respectively, and the correlation coefficients of monthly average results of these are 0.91 and 0.84, respectively. The diurnal variation of NO₂ concentration presents two peaks, i.e., in the morning and evening. Compared with the real-time traffic flow, NO₂ concentration is strongly positively correlated with traffic flow, and the correlation coefficient is 0.95. There is a significant weekend effect in the NO₂ concentration on working days relative to weekends.