The decision making theory finds its application literally at any field of science, especially at geosciences, because working with natural resources requires the most accurate tools. This paper considers one question of the given theory, which is called the solution priority problem. The priority problem in multi-object optimization is quite complex, many authors understand it in their own way. Perhaps this is because now the theory of multi- purpose optimization is in its infancy: there is no holistic understanding of the priority problem from its definition and task to its consideration. However, this work is not intended to bring final clarity to this issue, this task should be solved in the near future.There are numerous approaches to define improvability of the given solution, but this work considers only one of it. The considered approach can be applied for defining of solution improvability in the field of multi-objective optimization. This approach is based on applying of simple preference relation of one solution to another one...