The understanding of the methylation process was important for the management of paddy soils contaminated by mercury (Hg). The dynamic characteristics and the equilibrium time of methylmercury (MeHg) production in paddy soils were still poorly understood. Predictive models of MeHg production is necessary to demonstrate the major controlling factors and the extent of Hg methylation in paddy soils. Samples of eighteen paddy soils with varying soil properties were spiked with inorganic mercury and subjected to a 90d flooding period in this work. Soil pH and Eh were measured in situ at intervals and soils were sampled for the analysis of MeHg. The methylation rate of mercury increased with flooding time and reached to a relatively steady state at 30d of incubation with range from 0.08% to 2.52%, and was significantly correlated with the in situ soil pH and Eh. The elovich equation could well describe the kinetic production of MeHg. The MeHg production could be well predicted by the in situ soil pH and Eh of the flooded soils, as well as the content of organic matter of air-dried soil samples and flooding time. The two predictive models explained 78% and 68% of the variability respectively. The results suggested that the methylation of inorganic mercury in paddy soils after flooding can be predicted as a function of routinely-measured soil properties and flooding time. The results in the present study provided insight into the extent and equilibrium time of MeHg production and the associated risk assessment of Hg contaminated paddy soils.