Abstract: Abstract: To explore drought resistant effects of water-retaining agent, straw mulch and plastic film mulch between lines on osmotic substances and plasmas membrane system and yield of potato under dry farming, potato variety 'Shepody' was used, and totally six treatments such as straw mulch, plastic film mulch between lines, control group, and combined with water-retaining agent were set in the field experiment. The results showed that the value of plasmas membrane permeability was larger at seedling stage, then decreased and increased again from tuber bulking stage. Contents of proline and malonaldehyde presented a gradual increment trend in different growth stages, but content of soluble sugar showed a single-peak curve change. Lower contents of osmotic regulation substances and plasmas membrane permeability were observed in the treatments of plastic mulch between lines combined with water-retaining agent, water-retaining agent, straw mulch, and straw mulch combined with water-retaining agent, all these treatments released drought stress efficiently. Potato growth anaphase, till starch accumulation stage, proline content, soluble sugar content, plasma membrane permeability and malondialdehyde content changes were relatively stable. Compared with control group, the four indexes of plastic mulch between lines combined with water-retaining agent treatment decreased by 15.57%, 6.90%, 42.79% and 17.69%, respectively. The four indexes of water-retaining agent treatment decreased by 2.31%, 5.17%, 10.62% and 8.04%, respectively, which of straw mulch treatment decreased by 28.45%, 3.45%, 51.63% and 25.58%, respectively, and 25.14%, 12.07%, 49.17% and 22.58%, respectively for straw mulch combined with water-retaining agent treatment. At potato mature stage, soil moisture content under straw mulch combined with water-retaining agent treatments changed stably, 0-20 cm soil moisture content under water-retaining agent treatment was higher than that without water-retention agent treatments. Straw mulch combined with water-retaining agent, plastic mulch between lines combined with water-retaining agent and water-retaining agent treatments increased yield and commodity tuber rate of potato significantly (P<0.05). In all, straw mulch treatment decreased drought stress mostly, straw mulch combined with water-retaining agent, plastic mulch between lines combined with water-retaining agent and water-retaining agent treatments relieved drought stress obviously, and promoted potato growth and development and yield effectively.