Abstract: To understand the impact of hydrate reformation on gas production efficiency and mining safety during natural gas hydrate recovery, a numerical model for natural gas hydrate reformation in vertical wells under depressurization was established based on the theories of fluid dynamics and the finite difference method. The hydrate reformation region, spatiotemporal evolution characteristics, and hydrate amount under different depressurization strategies were simulated. Results show that the hydrate decomposition front and the interface of hydrate layers are the primary regions of hydrate reformation. Hydrate reformation at the hydrate decomposition front typically form earlier, with higher concentrations closer to the wellbore. The amount of hydrate reformation initially decreases then increases at the early recovery stage, stabilizes after slight declines at the middle stage, and then increases due to insufficient heat supply at the later stage. The depressurization mode has obvious influence on hydrate reformation. The stepwise depressurization (SD) mode, compared to one-step depressurization (OD) mode, can control the spatial extent of hydrate reformation at the hydrate decomposition front and delay the hydrate reformation time. The amount of hydrate reformation by OD mode is inversely proportional to the pressure reduction magnitude. However, for SD mode, the amount of hydrate reformation at the initial stage is inversely proportional to the pressure reduction magnitude but directly proportional to the pressure reduction magnitude at the later stage. These findings provide a theoretical basis for selecting natural gas hydrate exploitation strategies.