Abstract: Ground fissure is a typical urban geohazard in Xi'an, and heavy rainfall is one of the inducing factors for the settlement-deformation in loess ground fissure sites. Based on the indoor physical model test, the infiltration process of rainwater into the loess ground fissure site under heavy rainfall was simulated to reveal the settlement-deformation characteristics induced by rainfall infiltration in loess ground fissure site. The stress-strain state of soil layers was analyzed in ground fissure sites under heavy rainfall. Using distributed optical fiber monitoring technology, the generation process and influence range of secondary cracks were discussed. The results show that during the infiltration process of rainfall, rainwater converges towards the ground fissure, and the earth pressure increases significantly within the range of 0.5−0.7 m (5−7 m for the prototype) in the hanging wall of ground fissure. Pore water pressure near the fissure is elevated, with values increasing as the distance to the fissure decreases. The soil strain on both sides of ground fissures caused by rainfall shows a "saddle shape" change trend, with the strain increment gradually decreasing with depth. The presence of ground fissures induces differential settlement between the hanging and footwalls, causing the formation of secondary tensile fissures on the surface, oriented similarly to the main fissure, within approximately 0.7 m (7 m in prototype scale). This study provides a scientific basis for the foundation stability and fortification of buildings (structures) in loess ground fissure sites.