选择云南省水稻种植和气候典型区域，开展水稻作物系数及其规律观测试验研究。依据气象数据计算参考作物蒸发蒸腾量（reference crop evapotranspiration, ET0），同时基于田间实测水层数据建立田间水量平衡关系，分析计算水稻需水量（evapotranspiration, ETc），进而推求各典型区水稻作物系数Kc并研究其变化规律。结果可知，云南省各典型区水稻全生育期Kc值在0.99～1.18之间；各生育期呈现初期和末期较小、中期偏大的单峰曲线。Kc空间差异性没有明显规律，湿润、半湿润气候区略偏大，温凉气候区稍偏小；随海拔升高而减小但两者之间的关系并不密切；同一典型区Kc年际变化不大。研究结果可为今后云南水稻ETc计算提供重要参考和应用支持。

Ｒice planting and typical climatic areas in Yunnan Province are selected to carry out experimental research on rice crop coefficient ( Kc) and its regularity observation． On the basis of meteorological data，reference crop evapotranspiration ( ET0 ) is calculated． At the same time，water balance equation is established based on the data of water layer of the field，so as to analyze and calculate rice water requirement ( evapotranspiration，etc．) ． In this way，Kc in each typical area can be deduced and the changing rules can be studied． The results show that， the Kc value in the whole growth period of rice is between 0．99 and 1．18 in each typical region of Yunnan Province． A single peak curve with smaller initial and terminal stages and larger intermediate stages is presented． There is no obvious rule for Kc spatial difference． The humid and semi－humid climate zone is slightly larger，while the warm and cool climate zone is slightly smaller． Kc decreases with the increase in altitude，but the relationship between them is not close． The inter－annual variation of Kc in the same typical area is not significant． The results can provide an important reference and application support for ETc calculation of rice in Yunnan Province．