The invention discloses an 
irrigation requirement computation 
system and an 
irrigation requirement computation method under a climatic variation background. A historical 
data input module inputs collected climate parameters and 
crop information into a data forecasting module; the data forecasting module forecasts 
future climate parameters and 
crop information according to historical climate parameters and 
crop information; a sensor 
state control module selects a 
wireless sensor needing to be awakened and 
wireless sensor awakening time according to the forecasted 
future climate parameters and crop information, and collects the corresponding climate parameters and crop information in real time while the 
wireless sensor is awakened; and an 
irrigation strategy generation and execution module generates an irrigation strategy, and irrigates crops in time. The irrigation requirement computation 
system provided by the invention, 
irrigation water of the crops can be effectively managed while the wireless sensor has minimal network 
energy consumption; the computation method not only depends on the climate parameters and crop parameters, but also comprehensively considers economic efficiency of the crops and economy 
bearing capacity of farmers, so that utilization efficiency of 
water resources can be improved, and climatic variations can be effectively tackled; and meanwhile, consumption of network resources is greatly reduced by a dormant state of the wireless sensor, and a device life is improved.