Abstract: The multi-well crossing section's sedimentary system evolvement of Paleogene Xiaganchaigou formation ($E_3 xg^1$) to Neogene Shizigou formation ($N_2 s$) in Altun slope from Qigequan structure in the west to Niubiziliang structure in the east in western Qaidam basin indicates that ①Altun slope area develops fan delta, turbidite fan and shore lake bar deposit system from $E_3 xg^1$ to $N_2 s$; ② it develops an integral sedimentary cycle as a whole, in the early, $E_3 xg^1$ is a retrograding cycle and in the middle and late it is a progradational cycle; ③ the time that the each sedimentary system appears progradational cycle is different, of which Yue-3 well area develops the progradational cycle in the middle of the E3xg2, while Xichagou structure develops the cycle in the early of the $N_2 s$, in Yue-1 well area the cycle does not appear, and ④Niucan-1 well area develops retrograding cycle from the early of the $N_2$sy to the $N_2 s$. The development and evolution characteristics of sedimentary system in Altun slop area fully reflect that the Altun fault activity is of multistage, phase and local properties as well as out-of-step property to the full.

Key words: Qaidam basin, Altun slope, Paleogene, Neogene, depositional evolution, Altun fault