Delayed light emission (DLE), which mostly produced from chioroplast, can be an indicator of plant living ability. We have proved that environment stress can reduce the intensity of DLE. Our prior experimental results showed that there exists a linear relationship between DLE intensity and chloroplast concentration in a certain concentration range. Plant chloroplast's energy is sensitive to environmental stress. Considering the close relationship between DLE and environment stress we directly detected environment pollution by measuring DLE with a sensitive imaging system, which consists of a tungsten lamp excitation source, an ICCD digital camera, a controller and computer. Instrumental parameters (optical excitation time, optical source power, and exposure time) were adjusted independently to optimize measurements. Computer through controller collected all data. All images were analyzed with WINVIEW software. This experiments conducted with plant leaves treated with model acid rain (vitriol, pH 5.0) and exposed to moderately elevated troposphere sulfur dioxide environment demonstrated the environment stress could be inspected sensitively by measuring plant DLE. Our experimental results showed that when acid rain less than five zero could be inspected sensitively. It was also indicated that moderately elevated sulfur dioxide cause direct damage to the plant by reducing photosynthetic activity through partial stomata closure and other mechanics.