Abstract: The optimal irrigation quota of sectional subirrigation for cucumber in protected field was studied by measuring the yield and water use efficiency under different soil wetted ratios. The cucumber growth period was divided into two stages as earlier stage and later stage, and the irrigation was based on the upper irrigation control limit and lower control limit for each growth period. The results are showed as fellows: when the buried depth of subirrigation pipe is 25 cm, the planned wetting soil zone is 15-40 cm (25 cm depth), the upper irrigation control limit and lower control limit are 6 kPa (soil water suction) and 30 kPa, respectively, the optimal soil wetted ratio of planned wetting soil zone for earlier stage of cucumber is 0.37-0.38 (irrigation quota is 54-56 m3/hm2) and later stage is 0.34-0.37 (irrigation quota is 50-55 m3/hm2) for sandy clay loam, and at these wetted ratios the yield and water use efficiency are optimal.