Geothermal energy is considerably encouraged by governments because it offers a low-carbon renewable option to satisfy the long-term heat demand. However, to date research on systematic and scientific evaluations of the environmental benefits of geothermal heating is limited. Therefore, compared with the traditional coal-fired heating system, the cleanliness of geothermal heating is examined by employing the life cycle assessment approach in this study. Results show that the environmental impacts of geothermal heating are considerably less than those of coal-fired heating, and geothermal heating with water reinjection is the most ideal scenario. Environmental benefits linearly increase with the injection rate growth of geothermal water. Compared with coal-fired heating for per GJ of heat generation, geothermal heating can lead to 77%, 76%, and 78% reductions in terms of particulate formation, carbon emission, and fossil energy depletion, respectively. The electricity consumption process is the main contributor to the overall environmental burden of geothermal heating. Instead of coal power for geothermal heating, the actual hybrid electricity of China in 2017 (i.e., 64.7% coal power, 18.6% hydropower, 4.7% wind power, 1.8% solar energy) can lead to 27%, 33%, and 27% reductions in fossil depletion, carbon emission, and particulate formation for per GJ of heat production, respectively. These findings not only indicate the feasibility of using geothermal resources to address carbon emissions, energy crisis, and air quality issues, but also demonstrate benefits for human health and ecosystem quality. Furthermore, the results highlight the importance of generating electricity with clean energy in geothermal heating. Thus, generating electricity with clean energy instead of coal is necessary to further reduce the environmental impact of geothermal heating.