By Combining the variation of meteorological factors, it is analyzed the impact of climate change on water requirement of main crops in Nanjing, China and it is presented some measures to address the impacts of climate change. For achieving this goal, water requirement of crops in Nanjing from 1951 to 2005 is calculated with the method of Mann-Kendall. Combining the variation of meteorological factors, the paper analyzes the impact of climate change on water requirement of main crops in Nanjing and put forward some measures to address climate change. The data show that the decrease of water requirement of summer crops, such as rice, cotton and corn, is related with the insignificant increase of summer temperature, increase of rainfall, drop of sunshine hours, and slowdown of wind speed. While the increase of water requirement of winter wheat and canola is mainly related to the highest growth rate of winter and spring temperatures, the effect of drop in sunshine hours and slowdown in wind speed is not enough to offset that of the increase in temperature and the reduction in humidity. The cropping system is affected by temperature, which may bring the increase of total crop water requirement. Thus, water-saving irrigation, especially water impoundment for controlling irrigation is necessary to reduce irrigation and drainage quota, weaken greenhouse effect and reduce the impact of climate change on the rice production.