The development of sustainable and environmentally friendly defoliants has become a critical area of research due to the increasing demand for eco-conscious agricultural practices. Traditional chemical defoliants used in cotton harvesting have raised concerns over their environmental toxicity and adverse health effects. In this context, the calcium chlorate–monochloroacetic acid–triethanolamine–water system has emerged as a promising alternative, offering a less toxic and biodegradable solution. However, the solubility and crystallization behavior of this system, particularly under varying temperature conditions, remain poorly understood, limiting its large-scale application in the field. This study investigates the solubility diagrams and crystallization phases of the calcium chlorate–monochloroacetic acid–triethanolamine–water system across temperatures ranging from -52°C to 47°C. The goal is to optimize the defoliant formulation by identifying key phase boundaries and new crystalline phases. The study identified several crystalline phases, including Ca(ClO₃)₂·6H₂O, Ca(ClO₃)₂·4H₂O, and Ca(ClO₃)₂·2H₂O, as well as a novel compound, ClCH₂COOH·Ca(ClO₃)₂·(C₂H₄OH)₃N, which was confirmed through infrared spectroscopy (IR) and scanning electron microscopy (SEM) analysis. These findings provide valuable insights into the phase behavior of this system, potentially leading to the production of more efficient and sustainable defoliants for the cotton industry. Future research should focus on scaling up these results for field applications and exploring additional environmentally friendly compounds to further enhance agricultural sustainability.