An accurate and reasonable division scheme of operation periods is the premise and foundation for formulating metro train operation plans, and it is also an important way to improve metro operation efficiency. The feature vectors of passenger flow are constructed to divide metro operation periods. At an interval of 10 min, the operation period in a day is segmented, and the feature vectors of all the periods are constructed according to the characteristics of passenger flow changes in their corresponding periods. The K-means algorithm is used for clustering, and the results are evaluated by cluster evaluation indicators such as elbow method and silhouette coefficient to determine the optimal number of clusters, obtaining the optimal division scheme of operational periods. Finally, the division scheme of operation periods of Line 1 of Fuzhou Metro is given as an example, which verifies the feasibility of this method.