Shuanghuaishu ground fissures in Sanyuan County, ones of over 200 ground fissures developed in the Weihe Basin, are well-known for their sudden occurrence, which often cause severe damage to the infrastructures after heavy rainfall. In order to reveal the origin of their formation, the geological background, developmental characteristics and genetic mode of the Shuanghuaishu ground fissures were investigated in details by surveying, mapping, trenching, geological drilling, geophysical prospecting and field water immersion. The fissures are almost parallel with a NE50°–NE65° strike, and the obvious linear length is 800 m. These characteristics are well consistent with the secondary faults of the Liquan-Pucheng-Heyang fault. The fissures cause damage to buildings and farmlands in the form of a horizontal tensile crack and subsidence. The deeper the stratum is, the bigger fault displacement of the stratum it will be, so these fissures possess the characteristics of synsedimentary faults. Regarding their genesis, the fissures were generated under the coupling action of multiple factors. The regional extension caused secondary faults of the Liquan-Pucheng-Heyang fault to slip, resulting in a fracture system in the surface strata. During the period of heavy rainfall, large volumes of water seeped into these hidden fissures, causing a strong erosion and washout effect on the soil filled in the fissures. This process promoted the formation of the current ground fissures.