It is a new method for detection of environmental BTEX in the atmospheric pressure using the technique of laser ionization . The features of the method is high speed, real-time and on-line detection of the concentrations of environmental BTEX . The instrument is simple and does not need complicated vacuum system. Its detection sensitivity is below 5 ppb, time-resolution is 4 s. This method is especially suitable to measurement of exhaust gas of vehicle by roadside. The present paper gives an introduction to the systematic structure, major parameter and some results obtained from a monitoring of atmospheric environmental BTEX in the case of different traffic. The pollution would be more heavy when the traffic is busy, on the contrary, it would be light.