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With the aim to obtain a reasonable organic-inorganic fertilizer combination for high maize yield and reduce nitrogen leaching loss, field experiments and simulation were conducted by using the DeNitrification-DeComposition (DNDC) model to study the effect of replacing inorganic nitrogen with different ratios of organic nitrogen on maize yield and nitrate leaching loss. Six treatments were applied: no nitrogen (CK), only inorganic nitrogen (U1), and inorganic nitrogen with 25%, 50%, and 75% organic nitrogen (U3O1, U1O1, and U1O3), and only organic nitrogen (O1). The model was calibrated by using U1 treatment from 2018 to 2020 and it was verified by using the other treatments. The results showed that the DNDC model accurately simulated crop yield (NRMSE <5%) and nitrate nitrogen leaching loss (NRMSE<15%). In addition, the model was used to simulate and evaluate the effects of different management measures on maize yield and nitrate leaching. On the basis of the U1 treatment, the results revealed that increasing the application of inorganic nitrogen can decrease crop yield and significantly increase nitrate leaching. Increases in the amount of organic nitrogen, irrigation and frequency of inorganic nitrogen fertilizer application can increase maize yield and nitrate nitrogen leaching loss. With a pure nitrogen application rate of 240kg/hm2, as the proportion of organic nitrogen was increased, maize yield was first increased and then decreased, and nitrate nitrogen leached loss was gradually decreased. Overall, when the ratio of organic-inorganic nitrogen was 3∶2, crop yield reached the highest value (12578kg/hm2), and nitrate nitrogen leaching loss was also acceptable (15.7kg/hm2). This ratio was the optimal combination of organic and inorganic nitrogen for the study area.