A new reduction strategy for quantum dynamics study on the motion of large periodic cyclic molecules is proposed. On the basis of the path-integral quantum mechanics

in this work we show an equivalence relation between large periodic cyclic molecular motion and monomer motion. And hence

to computational study the large molecular motion based on the existing computing resources

only the motion of a single monomer needs to be accurately calculated. This strategy may greatly reduce the system degree of freedom and hence the computational cost

which implies an improvement of the computational cost efficiency.