By using the data of 20 meteorological stations from 1971 to 2004，the region distribution and its climatecharacteristic of heavy fog along the first - class highway in Gansu province were analyzed. The results show that heavy fog occurring along the highway presents not only obvious regional difference，but marked yearly，seasonal，day and night，and local changing characteristics. So the different forecast service periods for heavy fog in different sections of the highway are put forward，so as to provide the basis for heavy fog forecast along the first - class highway in Gansu province