This paper researches the effection of symmetry reduction to the numerical integration for holonomic system. Through numerical experiment, there is not essential effection for numerical integrator when system is reduced to lower dimension. But under the reduced system, it can effectively decrease the difficulty of writing program and the time of computation. So for the complicated dynamical system, it should be firstly reduced by symmetry methods and obtain the dynamical system with less degree of freedom, then the dynamical nature of system can be researched under the reduced system.