Abstract: It is important to improve the realtime irrigation forecasting precision by predicting realtime water consumption of cotton mulched with plastic film under drip irrigation based on meteorological data and cotton growth status. The model parameters  for calculating ET₀ based on Hargreaves formula were determined using historical meteorological data from 1953 to 2008 in Shihezi reclamation area. According to the field experimental data of growing season in 2009-2010, the model of computing crop coefficient K_c was established based on accumulated temperature. On the basis of crop water requirement (ET₀) and K_c, a realtime irrigation forecast model was finally constructed, and it was verified by the field experimental data in 2011. The results showed that the forecast model had high forecasting precision, and the average absolute values of relative error between the predicted value and measured value were about 3.7%, 2.4% and 1.6% during seedling, squaring and blossomboll forming stages, respectively. The forecast model could be used to modify the predicted values in time according to the realtime meteorological data and to guide the water management in local filmmulched cotton field under drip irrigation.