A strong sand-dust storm occurred in the Tarim Basin during the period from April 10 to 11 in 2006. This paper, using NCEP reanalysis data(horizontal resolution 1°×1°) and the simultaneous conventional observational data, analyzed its climatic background, circulation situation, helicity, divergence, temperature advection and frontogenetical second circulation. The circulation dynamical structure of this type of dust-sand storm was opened out: ①The Caspian ridge, Ural ridge and Xindidao ridge pile up, which causes the polar cold air entering into the Tarim basin and results in sand-dust storms in large extent; ②The eruptive and violent development of west cold Siberian high pressure is the principal cause of strong sand-dust storms; ③The dry and warm situation of the basin in prophase of sand-dust storm provides the advantageous thermal condition for sand-dust storms occurring; ④The vertical distribution of helicity over the sand-dust storm area is negative at the high level and positive at the lower, which imply that the strong rotating climbing movement is the dynamical condition of sand-dust storm occurring; ⑤The downward branch of the circulation in high jet entrance bring the high momentum to the lower layer, increasing the wind speed in the middle and the lower troposphere, pushing the cold front moved southward, and ultimately driving sand-dust storms broke out.