This chapter presents new methods and software system SOSNA intended for the parameter optimization of heat supply systems. They make it possible to calculate large-scale systems which have a complex structure with any set of nodes, sections, and circuits. A new methodological approach to solving the problem of the parameter optimization of the heat supply systems is developed. The approach is based on the multi-level decomposition of the network model, which allows us to proceed from the initial problem to less complex sub-problems of a smaller dimension. New algorithms are developed to numerically solve the parameter optimization problems of heat supply systems: an effective algorithm based on the multi-loop optimization method, which allows us to consider hierarchical creation of the network model in the course of problem solving; a parallel high-speed algorithm based on the dynamic programming method. The new methods and algorithms were used in the software system SOSNA.