Abstract: The paper aims to quantitatively estimate the effect of drought which continued for a period on meteorological yield of summer maize. The WOFOST model was used to carry out the estimate by adopting the measured meteorological data before the estimating day and the average meteorological data of the recent 5 years after the estimating day forming a new sequence of data, and designing 3 kinds of scenarios and 4 kinds of treatments. The results showed that: on the estimating day, the yield reduction rate of summer maize changed greatly between 14%-64% in different drought areas only under rainfall. It was between 47%-64% in heavy drought area and 28%-50% in middle drought area, while 14%-47% in light drought area. The yield reduction rate of summer maize dropped sharply with irrigation, under which the drought stress influence was little. With adequate irrigation, there was nearly no yield reduction in the light drought area and the yield reduction in heavy drought area was between 10%-38%. Verified by actual meteorological data, the model was more accurate for the light drought area and middle drought area than for the heavy drought area. Therefore, the crop model can be used to quantitatively estimate the effect of continuing drought for a period on the meteorological yield of summer maize.