Abstract: Abstract: Biochar is widely used as a promising green and cost-effective alternative for soil amendment, because of its agronomic benefits in soil carbon sequestration and facilitating nutrient cycling, and improvements in water use efficiency and crop growth and yield. The absorption of water and nutrients for plant from soil is directly influenced by root morphology, and root morphology plays a significant role in plant growth and water use efficiency. But there is limited information on the interaction among root morphology and plant growth, water use efficiency under biochar application. Hence, in order to investigate the effects of biochar on winter wheat growth, yield, water use efficiency and root morphology, in this study, a one-year field experiment with different application amounts (0, 20, 30, 40, 50 and 60 t/hm2) of wheat straw biochar (pyrolysis temperature of 600℃) was carried out under subsurface drip irrigation condition. The preliminary results showed that the tiller number, efficient spike number and yield of winter wheat were significantly affected (P﹤0.05) by biochar, increased by 1.6%-4.9%, 0.7%-1.5%, and 1.0%-5.9%, respectively. Plant height and spike length were not affected by wheat straw biochar. Grain number and 1000-grain weight were significantly increased (P﹤0.05) only under the treatments of 30, 40, and 50 t/hm2 application of wheat straw biochar. Grain number increased by 4.7%, 8.6% and 2.7%, respectively and 1000-grain weight increased by 5.6%, 8.0% and 5.0%, respectively, which showed biochar application could effectively increase winter wheat yield through the increase of tiller number, efficient spike number, grain number and 1000-grain weight. The water consumption of winter wheat decreased significantly (P﹤0.05) with the increase of application amount of wheat straw biochar, which decreased by 2.6%, 7.0%, 7.7%, 9.1% and 9.4% respectively under the biochar application amounts of 20, 30, 40, 50 and 60 t/hm2. The water use efficiency increased from 17.06 to 17.69-19.57 kg/hm2·mm with the increase of application amount of wheat straw biochar, and the highest value was obtained under the treatment of 40 t/hm2. The root morphology characteristics of winter wheat were significantly affected by wheat straw biochar. The application of wheat straw biochar increased total root length of 0-20 and 20-40 cm for winter wheat by 2.8%-14.6% and 8.4%-21.2%, respectively, increased root surface area by 5.6%-19.5% and 1.9%-13.6%, respectively and increased average root diameter by 0.4%-4.1% and 1.4%-2.0%, respectively. The application of wheat straw biochar had less positive effect on average root diameter of winter wheat, compared with total root length and root surface area. In comparison with other levels of biochar application, the treatment of 40 t/hm2 was more effective in the improvement of winter wheat root growth. The root morphology characteristics were very significantly correlated with the yield of winter wheat (P<0.001). Compared to other application amounts of wheat straw biochar, the treatment of 40 t/hm2 had the most significant impact on the growth, yield, water use efficiency and root morphology characteristics of winter wheat. This study provides references for scientific and rational utilization of biochar in agriculture.