Along with increasingly fierce competition, demand change becomes faster and demand is apparently time-varying. This paper, based on time-varying demand, probes into optimization of shortage times under equal-cycle reorder and optimization of shortage times and reorder times under non-equal-cycle reorder, especially, the paper studies decision-making models of local optimization and global optimization, and finds that non-equal-cycle reorder and global optimization of reorder times can effectively decrease inventory cost. Meanwhile, this paper analyses relationship between performance of reorder time optimization and both the parties＇ reorder frequency and demand time-varying