Abstract: Crop water requirement in north China is critical in farm water cycle. The paper aims to investigate the variation tendency of water requirement of main crops in Shanxi Province and their response to climate warming. Based on daily meteorological data of 39 weather stations in Shanxi Province during 1961—2010, the water requirement of two crops was calculated using Penman-Monteith equation modified. For both corn or wheat, water requirement had two clear changes with a dividing point in 1982, the water requirement of corn first showed a weak upward trend (1961—1982; 4.8 mm/10 a) and then showed a slight downward trend (1983—2010; -1.0 mm/10 a); meanwhile, wheat water requirement in both the two stages showed a significant upward trend (20.6 mm/10 a and 17.1 mm/10 a), but the increase was not continuous. The average water requirement value of the two crops in 1983-2010 was less than that in 1961—1982. The decrease of water requirement of corn exceeded that of wheat. Regional differences were noted for the impact of warming climate on crop water requirement. Climate warming had more impact on crop water requirements in the frigid zones than warm regions. On the other hand, the impact of warming climate on corn water requirement was the highest in arid regions, followed by semi-humid regions, and then semi-arid regions. Variation of crop water requirement was closely related with the local crop yield, the result showed that corn water requirement and corn yield were significantly and negatively correlated, therefore, variation of corn water requirement could effectively reflect or predict the changes of crop yield.