The January 2 snowstorm in 2000 in Yinkou,Northeast China is analyzed based on the NCEP 6-hour interval reanalysis data.The analysis shows that the snowstorm occured under the large scale circulation background of two-trough-two-ridge over the Eurosian continent,and resulted from the coupling of the upper level westerly jet and the low level southwesterly jet.The upper-level jet created the dynamic instability condition and the low-level jet played the vapour provider of the snowstorm and the trigger of convective instability energy release.The convective instability layer in the storm stretched from the ground surface upwards to the altitude of 850⁸00hPa,and the snowstorm region has a better correlation with the negative value core of moisture potential vorticity(ζ_MPV).The transfer of moisture potential vorticity by the low-level jet enhanced the conditional symmetric instability in the snowstorm region,thus favorable for the genesis of the snowstorm.