Abstract: APSIM model was carefully calibrated and validated by using measurement data and meteorological data over the same period at four sites in Ningxia. The results showed that there were good correlations between simulated values and measured values with determination coefficient R2 ranging from 0.82 to 1, and D value ranged from 0.78 to 0.99. Based on this, different irrigation amounts were used to simulate Lucerne dry matter production (GY), evapotranspiration (ET) and water use efficiency (WUE). The results showed that irrigation was the important factor of Lucerne production in semiarid area of Ningxia. 200 mm irrigation amount was the turning point of Lucerne dry matter production from increasing to reducing. Lucerne in different growing stage showed different sensitivity to water. The biggest irrigation amount was 50 mm in branching and budding stage, and production would decrease when irrigation amount more than 50 mm. Evapotranspiration (ET) linear significantly correlated to irrigation amount, and determination coefficient R2 reached 0.826 and P<0.01. Water use efficiency could not invariably increase with the increasing irrigation amount, it would reach 54.2 kg/hm2mm when irrigation increased to 100 mm, then reduced. While more irrigation amount went against the improving of water use efficiency.