Magnetorheological fluids (MRFs) are smart materials characterized by reversible magnetic-field-controllable properties and millisecond-level response times. They hold significant application value and vast potential in various fields, including vibration control, military equipment, vehicle damping systems, and biomedical devices. Despite decades of theoretical research, the practical engineering applications of MRFs continue to encounter multiple technical challenges. Traditional oil-based MRFs tend to experience a sharp increase in viscosity in low-temperature environments, leading to poor flowability and considerable attenuation of the MR effect. Furthermore, the performance of these fluids deteriorates over time due to the volatilization of the oily base carrier liquid. Additionally, issues such as sedimentation and caking, stemming from the density differences among magnetic particles directly impact the long-term stability of devices utilizing MRFs. This study focuses on enhancing the low-temperature adaptability and optimizing the sedimentation stability of MRFs. In terms of base-liquid selection, an ethylene glycol-water mixed solution was used to replace the traditional oily base carrier liquid. The aim is to expand the working capacity of MR materials in low-temperature environments. Regarding the sedimentation problem, through comparative experiments, sodium hexametaphosphate (SHMP) and hydrophilic nano-silica (SiO2) were screened as additives to improve the sedimentation stability of MRFs. Sedimentation stability tests showed that the MRF samples incorporating SHMP and SiO2 had only a small amount of sedimentation after long-term static storage. Rheological characterization further revealed that the prepared MRF exhibited typical Newtonian fluid characteristics under zero-magnetic-field conditions, and the shear stress increased rapidly when a magnetic field was applied, showing excellent controllable rheological properties. This study successfully developed an ethylene glycol aqueous-based MRF that combines low-temperature applicability with high sedimentation stability.