Abstract: Many crop-growth models have been established for predicting the effects of soil, water and nutrient on grain/biomass yield and water productivity of different crops. However, most of the crop-growth models were still at research stage and only few have been applied in actual production processes due to limitations in simulation input data. To predict the influence of water and nutrient on yield, biomass and water productivity of oil flax, a water-driven crop model, AquaCrop model, developed by FAO was used to simulate and validate the growth of oil flax under different irrigation and nitrogen/phosphorus levels. In the study, field experiment with 9 nutrients treatments (3 nitrogen levels and 3 phosphorus levels) under four irrigation levels were conducted at Yuzhong Field Station. The experimental data collected in 2011 was used to simulate yield, biomass and canopy cover and data collected in 2012 to validate the model. The performance of model was evaluated from model efficiency (E), determination coefficient (R²), root mean square root (RMSE) and mean absolute error (MAE). The results showed that the prediction errors of the calibrated yield and biomass of the AquaCrop model under different irrigation and nitrogen/phosphorus treatments were 0.97 < E < 0.99, 0.11 < RMSE < 0.33 and 0.11 t·hm^-2< MAE < 0.42 t·hm 2. These were in accordance with measured data in the experiment study in 2012 (0.96 < E < 0.99, 0.11 < RMSE < 0.42 and 0.11 t·hm^-2< MAE < 0.39 t·hm^-2). Furthermore, the simulated results of canopy cover and biomass matched observed values. The predicted yield of oil flax by the AquaCrop model was more accurate under intensive irrigation treatment than under deficient irrigation treatment. The FAO AquaCrop water-driven model had higher simulation precision when oil flax was simulated in Northwest China with different irrigation treatments and field management practices. The model showed broad application prospects in China.