Abstract: With the gradual expansion of the scale of the power system and the increase of the load density, the problem of excessive short-circuit current has gradually become an important factor restricting the development of the power grid. A short-circuit current limiting measure based on the dynamic adjustment of system topology has not any influence on the normal operation of the system but only adjusts the system structure during the fault period. However, its introduction may have a certain impact on the reliability of the system. This paper studies the graph theory modeling and calculation methods of the power grid connectivity, establishes a system topology simulation example with a typical power grid as an example, and analyzes the short-circuit current suppression effect and its influence on the system reliability under different topology adjustment methods. The research result shows under the typical connection of a 220kV system, the topology adjustment switch arranged at the bus section is the first choice under consideration. It has better suppression effect for the short circuit current, and the impact on the system reliability is relatively small.