Smog pollution in the ground layer atmosphere over Xining city,Qinghai province was analysed with the NOAA 12 remote sensing images obtained in cloudless dawns from 1993 to 1997. First,smog characteristics of the remote sensing images were studied. Second,the latitude and longitude of the smog area was calculated with these characteristics. Finally,the generation conditions of smog pollution over Xining city were given,and it suggested that the ground layer atmosphere over Xining city in winter is favourable to smog generation.