This paper studies two typical ways to use multigrid methods in CFD simulations. One is implementing multigrid methods in CFD softwares start from scratch, and the other is calling multigrid methods from existing libraries. The experimental results on two benchmark cases, the lid-driven cavity flow and the flow around a cylinder, show that the solving performance and parallel scalability of calling multigrid methods from third-party libraries are much better than that of using the multigrid methods implemented in CFD softwares. The result not only provides some guidances for users who try to simulate with multigrid methods, but also gives a possible recommendation for the development and application of softwares for exascale systems. It is a more clever and efficient way to develop softwares on massively parallel systems based on some existing packages and libraries, which reduces the degree of coupling between different functional modules and improves the development efficiency.