Abstract: The landslide is a common geological disaster, and the loess landslide instability induced by irrigation is one of the common geological disasters. Irrigation function changes the balance of ground water and reduces the resistance strength of soil mass, resulting in the occurrence of loess landslides. For the loess landslide No.13 of Jiaojiayatou, centrifugal model tests on landslide instability mechanism under irrigation effect are carried out. The deformation characteristics, stress levels and failure modes are revealed. The preporation of centrifugal model considers the influences caused by "particle size effect" and "size effect". The results show: (1) With the increase of loading time and centrifugal acceleration, the settlement, earth pressure, pore water pressure of model slope all gradually increase. (2) The slope settlement gradually decreases from the slope top to the toe. The maximum vertical displacement is 33.38 mm. The soil pressure of slope gradually increases from the slope top to the toe. The largest earth pressure is 320 kPa, the pore water pressure is the largest at the slope top, that at the toe is followed, and that in the middle is the smallest, and the maximum pore water pressure is 157.08 kPa. (3) The slope emerges two failure modes: one is creep deformation of the toe and pressure-induced crack of the top, the other is shear slip of the slope.