The work aims to improve the optimization efficiency of storage location of the online retail business subject to the rapid change in demand and large fluctuation. The composite rules-based dynamic storage location assignment strategy was studied based on the data warehouse and data mining technology. The date integration analysis, index calculation, rule generation and storage location assignment of such storage location assignment were analyzed. Moreover, the zone calibration algorithm and rule generation algorithm were designed to generate the storage location assignment rule set. The composite rules-based dynamic storage location assignment could save the picking distance, and its picking efficiency was insensitive to the change in demand. Numerical experiments show that, compared with the traditional storage location assignment strategy, the composite rules-based dynamic storage location assignment system can get better results, and especially in the larger-sized average order with high demand skewness, the effect is more obvious.