This paper aims to help developers have a deeper understanding of simulation modeling and solving through the description for the solution process of Differential Algebraic Equations (DAE) in the simulation system, which is convenient to analyze and find the problems in simulation modeling. Using the index reduction technology, the solving problem of DAE equation was transformed into the solving problem of ODE equation, and the existing technologies such as numerical solution and error estimation were used to solve it. The advantages and disadvantages of the existing technologies of DAE system in key links such as index reduction, numerical solution and error analysis were summarized by analyzing and summarizing the existing technologies. The key research directions in the field of simulation modeling in the future are pointed out.