Utilizing the NCEP (1°×1°) reanalysis data, the causes of the floating dust on 4 and the blowing sand weather on 5 May 2017 are analyzed. It shows that the Mongolia cyclone, which rapidly developed under favorable circulations background, together with the cold front, resulted in a wide range of strong sand and dust weather in the middle and east of the Inner Mongolia Autonomous Region from 20:00 on 3 to 08:00 on 4 May. Through the upper air current, the dust was transported to North China from 20:00 on 4 to 08:00 on 5 May. The dustfall and strong downward flow led to a wide range of floating dust weather in North China. Influenced by northwestern cold air, the transversal trough was converted into a vertical one, the cold front speeded up southward, and the sand and dust were transported to Dezhou and hit there from 08:00 to 14:00 on 5 May. Based on the simulation results of backward trajectory of air mass using HYSPLIT model, the transportation modes and pathways of these two kinds of sand and dust weather were clearly verified. Through the analysis of synoptic systems, physical quantities and meteorological factors, the changes of intensity and position of synoptic systems in Mongolia and the central Inner Mongolia Autonomous Region were found to directly affect the types of the sand and dust weather. The change of upper air current was well correspondent to the types of the sand and dust weather.