Abstract:One approach to improve summer soybean yield and water use efficiency (WUE) is to identify appropriate crop population distribution pattern. The objective of this investigation was to investigate the effect of different population distribution patterns on yield, yield components, and WUE in summer soybean. The experiment was carried out from June to September in 2007 at Agronomy Experimental Station of Shandong Agricultural University. The summer soybean (Glycine max cv. Ludou 4) was grown under 5 distribution patterns with the same plant population(3.09×105plant/hm2).The row spacing(cm) plant spacing(cm) was A: 18 cm×18 cm, B: 27 cm×12 cm, C: 36 cm×9 cm, D: 45 cm×7.2 cm, and E: 54 cm×6 cm respectively. Yield, leaf water character, and water use efficiency were affected by the population distribution of summer soybean. The yields in case of A and B were significantly higher than in case of D and E (P<005), while no significant differences were found among other treatments; The number of productive pod, seed per plant, and 100-seed weight declined gradually with the increase crop spacing; The yield had a positive correlation with seed number in main stem(R=0.994**) and 100-seed weight(R=0.893*); Leaf relative water content(RWC), water potential(Ψw), and osmotic potential(Ψs) declined gradually with crop growth, The average of RWC, Ψw and Ψs in case of A and B was all significantly greater than in case of D and E, Ψw in case of E was obviously lower than other treatments at noon in the daytime; The WUE was negatively correlated (R=-0.935*)with the row spacing, but positively correlated (R=0.997**) with the yield. The WUE in case of A and B was significantly higher than other treatments (P<0.05), and that of D and E was significantly lower than in case of B (P<0.01).These results indicate that the summer soybean population with relatively uniform distribution would improve the yield components and leaf water conditions, consequently develop high yield, and increase WUE.