Loess, an aeolian and unsaturated deposit, is highly sensitive to water. It can swiftly cause a series of detrimental effects including soil erosion, water and soil losses, and slope instability under the action of water and loading. Consequently, enhancing the water stability of loess is paramount for mitigating these issues. This study systematically investigates the effect of sisal fibers on the disintegration characteristics and microstructure of Q3 Malan loess using a self-designed disintegration apparatus and scanning electron microscope (SEM). In addition, the disintegration ratio, rate, and microstructure between untreated loess and loess amended with sisal fibers are compared and analyzed. A quantitative analysis was conducted to assess how the sisal fiber dosage and curing period influence the disintegration characteristics of sisal fiber-amended loess. The results show that sisal fibers effectively enhance the resistance of soil to disintegration, with this resistance intensifying with increasing sisal fiber dosage and extended curing periods. Notably, when the curing period reached 3 days and the fiber dosage reached 0.45%, the sisal fiber-amended loess did not disintegrate. The incorporation of sisal fibers results in a decrease in soil pore area, with a greater fiber dosage leading to a lower pore area. In addition, sisal fiber can promote the formation and accumulation of organic matter in the soil, which can not only improve the bonding energy between soil particles but also facilitate carbon sequestration. This study underscores the potential of sisal fiber as a green and environmentally friendly modifier for loess, offering a promising solution for mitigating soil erosion and slope instability by enhancing the resistance of the soil to water-induced disintegration.