There are two decollement strata in southwestern depression of Tarim Basin: one is 500 m Middle Cambrian salt-gypsum layer, and another is 100~700 m Lower Paleogene gypsum mudstone with limestone and dolostone. The decollement structure is the most important structural style. The decollement structure and other structural styles consist of four kinds of structural assemblages in section: 1 ) decollement fault related fold; 2) imbricated decollement structure ; 3 ) wedging structure + reconstructed fault related fold; and 4) detachment fault + fault related fold. The structural modes of these structural styles are set up, which are significant to structural interpretation and identification of traps of complicated areas in southwest Tarim Basin.