Based on the CMAP global precipitation data and NCEP/NCAR reanalysis data from 1979 to 2002,the characteristics of seasonal and interannual variability of Vietnam precipitation is analyzed,and the influence of Somali cross-equatorial flow on Vietnam precipitation is also studied.Results show that southern precipitation has seasonal and interannual variability characteristics different from those of northern precipitation.Southern precipitation mostly happens in summer and autumn,and the two season rainfalls show an antiphase relation;while northern precipitation mainly concentrates in summer.The strength of Somali flow in summer has a good correlation with southern precipitation in summer and autumn,the former is a significantly positive correlation,and the latter is a remarkable negative correlation;however,the relationship between Somali flow and northern precipitation is not evident.Research also indicates that the correlation between the west wind over the equatorial Indian Ocean in summer and southern Vietnam precipitation is similar to Somali flow,therefore it can be inferred that through modifying meridional water-vapor transfer,Somali flow affects precipitation in southern Vietnam.