Abstract: Threshold for dust emission represents soil erodibility and becomes one of the important parameters in wind-erosion research. From the view of micrometeorology, the dust emission threshold friction velocity (u*t) and dust emission threshold wind speed (Ut) are defined as the value of friction velocity and wind speed when both of dust concentration and vertical dust flux begin to increase with friction velocity and last for half an hour at least. Using the observational data of sand-dust events in 2010-2013 spring over the Horqin Sandy Land area in Inner Mongolia, the evolution of dust concentration and vertical dust emission flux with friction velocity during the different dust emission period of sand-dust events (e.g. blowing dust events, sand-dust storm events, and severe sand-dust storm events) is analyzed. According to the definition, the values u*t and Ut over the Horqin Sandy Land area are determined to be 0.45±0.20 and 6.5±3.0 m/s, respectively. Meanwhile, the effects of different dust-emission criteria to the determination of dust emission thresholds are discussed. Comparing with the previous dust-emission criteria, the one used in this study can effectively exclude the influence of dust advection and deposition and reduce the simplicity and subjectivity of the criteria. This study can provide references to set up uniform dust-emission criteria in the future.