Abstract: Sowing winter wheat under smashed corn straw returning using rotary machine is the main mode of winter wheat cultivation in Southwest Shanxi Province. Winter watering can compact soil, accelerate corn straw rot and ensure safe wheat over-wintering. However, less study was reported on winter watering effect under condition of smashed corn straw incorporation using rotary machine. To explore optimal management of winter watering of winter wheat under this condition for development of strong seedling before winter, improve wheat growth, thereby increase grain water use efficiency and yield, an experiment was conducted in Yaodu District of Linfen City, Shanxi Province, China, to investigate winter watering time effects on winter wheat growth. Four watering time treatments were designed-November 10, November 25, December 10 (traditional watering time used as control) and December 25. No-winter watering was set for investigation of soil properties. Tiller and roots before wintering, photosynthetic characters, yield and water use efficiency of winter wheat under different treatments were investigated. The results showed that compared with treatment of non-winter watering, winter watering compacted soil and adjusted soil bulky density, which enhanced root closely touched to the soil and soil enzymes activities, thus enriched soil nutrition level and improved tillering and secondary root growth. The winter watering treatments compensated for winter wheat growth compared with control treatment. They increased stem and secondary root numbers before winter, and increased root dry weight per plant. Under early winter watering treatments, flag leave lifespan extended, chlorophyll content increased and photosynthesis enhanced. All these resulted in final head number increase by 1.66%-5.37%, 1000-kernel weight increased by 0.55%-3.03%. For sowing winter wheat under smashed corn straw returning using rotary machine, it was found that winter wheat yield under treatment of November 25 increased by 8.40% and water use efficiency increased by 5.76% (22.05 kg·mm^-1·hm^-2) at early tillering stage. In summary, under cultivation mode of smashed corn straw returning using rotary machine, proper early winter watering (in 25 November) was beneficial for formation of strong seedlings, high yield and water use efficiency of winter wheat.