From 30 December 2016 to 8 January 2017, a haze weather with PM2.5 as the main pollutant lasted for several days and severe pollution appeared in most areas of Shandong Province. Based on the observational data and ERAInterim reanalysis data, the weather background and boundary layer characteristics of the process are analyzed. The results show that the condition of horizontal zonal circulation at high altitude, the weak pressure field on the ground and the typical stable weather patterns, were conducive to the continuous haze. During the process, three cold air processes appeared. The intensity of cold air affected the change of haze. Weak cold air could not destroy the inversion structure near the surface. At the same time, weak cold air transported pollutants from upstream, which was favorable for the accumulation of pollutants. Strong cold air brought strong vertical movements and destroyed the stable weather situation, which facilitated the diffusion and the removal of pollutants. Under the stable weather condition, the boundary layer height was an indicative physical quantity for the haze. The change of boundary layer height and AQI had a lag negative correlation relationship, and thus the AQI index increased when the boundary layer height decreased. The existence of an inversion layer for a long time was an important condition for the continuation of the haze. In addition, due to geographical reasons, the low layer southeast wind increased the humidity and the reduction of inversion layer top height, which both led to the increase of pollutant concentration, so to aggravate the haze.