After water-soluble nickel (Ni) is added to soils, its bioavailability/toxicity, isotopic exchangeability, and extractability decline over time. Two separate semi-mechanistic models (Sqrt- and Ln-model), have been developed to predict short- and long-term aging of Ni added to soils. To continuously predict Ni aging in one model, a semi-mechanistic model (Erfc-model) was developed in the present study with description of diffusion process using a complementary error function. The developed Erfc-model could predict Ni aging processed for short- and long-term aging continuously with regression coefficients (R²) of 0.87 and 0.94, which were very comparable with that for Sqrt- (0.91) and Ln-model (0.89). Based on the Erfc-model, soil pH and aging time were two important factors that influencing Ni aging processes. Additional 45 soils that covering short- and long aging time were collected to validate the model. Strong correlation (R²=0.85) was found between the measured and predicted lability of Ni in soils with root-mean-square-error (RMSE) of 8.97%, illustrating that the Erfc-model could continuously predict short- and long-term aging processes of Ni added to soils. The model could be used as an alternative to normalize ecotoxicological data for driving soil environmental quality standards.