Based on daily observations from ground-level stations, information on national statistical offices, the aerosol optical thickness (AOD) as derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra spacecraft and monthly NCEP/NCAR reanalysis dataset, the winter spatial-temporal variations of haze during 1980~2016 in Shaanxi Province and its possible reasons of the increase were analyzed. The main conclusions were as follows:(1) The numbers of annual winter haze days averaged all sites was about 12d.The provincial annual winter haze days was above the normal in 1980~1993, below the normal in 1994~2012, and showed an evident increasing frequency during 2013~2016. The provincial annual average haze days was above 36d with high values at Guanzhong area in the winter of 2016. Light haze was the most common haze. (2) Based on geographical locations, the province was divided in to three sub-regions. The annual average haze days were very different in different sub-regions. The annual average haze days in Guanzhong Area was above 18d. The number of annual average haze days was about 10d during 1980~2016 in Southern part of Shaanxi Province. The number of annual haze days averaged all sites in Northern part of Shaanxi Province was about 3d during 1980~2016. The annual haze days of the three sub-regions showed same increasing trend during 2013~2016. (3) There was a heavy aerosol loading which was above 0.4 over Guanzhong area and the southern part of Hanzhong and Ankang during 2000~2016 in winter. The Guanzhong heavy aerosol loading area was highly consistent with the heavy haze days in Guanzhong area. (4) The east wind of lower troposphere from southeastern China was a factor for transporting the aerosol to Guanzhong Area in winter of 2013~2016. The increased AOD could enhance the haze phenomenon in Guanzhong. The increased potential temperature differences between 2013~2016 and 1980~2012 in lower troposphere could weaken the vertical diffusion of haze.