Abstract: The synthetic crop coefficients are evaluated by analyzing the experiment data on water requirement of rice in plastic film mulched dryland (RPFMD).In consideration of the effect of physiological and ecological indexes in RPFMD,the calculation formulas of the synthetic crop coefficient are proposed concerning on rice growth factors including canopy leaf area index,green leaves coverage of zenith angle,the effective fraction of soil surface shaded by vegetation and days after transplant.The calculation results are agreement with measured values,and the F test reaches an extreme significance level.The formulas are accurate enough to be applied to the calculation of actual evapotranspiration of RPFMD.