One fog and haze weather process was detected by an atmosphere fineparticle lidar and instruments of Beijing Weather Observatory. Combining the changes of surface observation and highlevel weather elements, this paper analyzes the meteorological conditions for the maintenance of this foghaze event. First, temperature continues to rise, humidity is above 50%, wind speed is basically below 2 m·s-1, such conditions of high humidity, light wind are not conducive to rapid spread of particulate matter. Second, persistence of inversion layer and weakened atmospheric convection prevents the diffusion of particles to high altitude causing massive accumulation of particulate matter. The above two main reasons result in persistence of the fog and haze process. The fog and haze process is eventually dissipated by the rain erosion to particulate matter, the role of wet deposition and the increase of surface wind arrival. From detection results of atmosphere fine particle lidar we found the fog and haze vertical height reduces very quickly. The detection results of the fine particle lidar and ground instruments are basically the same. However, comparing the detection results of the fine particle lidar and the Lband sounding radar, under the saturated vapor condition, the foghaze height detected by the fine particle lidar is lower.