The freshwater crisis is becoming a problem that restricts the development of human society and people's health. Purification of polluted water and seawater desalination are the effective ways to produce freshwater and solve this problem. Directional Solvent Extraction, a non-membrane methodology using specific solvents to extract freshwater from polluted or salty water, is becoming an emerging technique in the last decade. The directional solvent extraction process can utilize low-quality and low-temperature waste heat generated by thermal power plants and solar energy.This dissertation provides the research results about directional solvent extraction in different cases. Firstly, the study shows the feasibility of using fatty acids as working substances in treating water containing arsenic. Secondly, the study demonstrates that a specific ionic liquid can have a greatly enhanced performance in water yield and energy cost of seawater desalination. In this work, the experiment and computing simulation are combined. The studies both show the experiment result and the mechanism from the molecular level.