Abstract: Cucumis statirus L. is one of the vegetables which are not only in great need of water, but also sensitive to it. So it is very important to manage irrigation for realizing high yield and great efficiency. Therefore, the morphological characters, physiological and photosynthetic characteristics under different soil moisture were studied in this paper. The results are shown below: ① Under 80%~90% relative soil moisture(T3), it was much better in growth& development and root/canopy ratio, higher in per cucumber weight and yield, lower in malformation rate than those under lower relative soil moisture(T1: 60%~70%, T2: 70%~80%) and the difference of which between T3 and T1 ,T2 were greatly significant, but there was no significant difference between T3 and T4(90%~100%). If relative soil moisture was kept lower(T1,T2), some bad results came accordingly, such as slower growth, lower height, higher malformation rate of cucumber, lighter per cucumber weight and lower yield than those of T3. Contrarily, higher relative soil moisture(T4) also brought many disadvantageous results, such as expansive growth, lower water use efficiency, tremendous waste of water and comfortable environment for disease and insect pests. ② From the view of photosynthetic characteristics and diurnal variation, Net photosynthetic rate, transpiration rate, stomatal conductance and light use efficiency grew increasing with the increase of soil moisture. However, water use efficiency took on opposite trend when soil moisture got higher. The net photosynthetic rate, transpiration rate, stomatal conductance and light use efficiency of T2,T3 and T4 presented a double-peak curve and the first peak appeared at 11:00 o’clock, the second one came forth at 15:00 o’clock. Nevertheless, diurnal variation of photosynthetic characteristics mentioned above of T1 took on a single-peak curve, and the peak emerged at 10:00 o’clock, one hour earlier than that of T2,T3 and T4. The diurnal variation of water use efficiency presented descending trend on the whole.