In order to analyze the deformation and failure mechanism of canal slopes, the consolidated drained and consolidated undrained triaxial shear tests were carried out on the collapsible loess of an open-channel water transfer project in Xinjiang. The triaxial test shear curve was simulated by the improved Duncan-Chang model and compared with those obtained from the Duncan-Chang model and the hump-type cubic curve model. The results show that with the increase of confining pressure, the stress-strain curve and volume change curve of consolidated drained test change from softening type to hardening type. The stress-strain curves of consolidated undrained test are all hardening type, and the pore pressure curves are all softening type. The effective cohesion obtained by the consolidated drained test is greater than that obtained by the consolidated undrained test, and the effective internal friction angle obtained by the consolidated drained test is slightly different from that obtained by the consolidated undrained test. There are nine parameters in the improved Duncan-Chang model. The Duncan-Chang model cannot reasonably describe the softening triaxial test curve, and the hump-type cubic curve model has a poor fit to the strong softening triaxial test curve, while the improved Duncan-Chang model can better describe various types of triaxial test curves of collapsible loess and has good accuracy.