A field experiment (2008–2009) was conducted at the Heyang Dryland Farming Experimental Station in Shaanxi Province of China to determine the effects of straw mulch rates on soil moisture and spring maize (Zea mays L.) yield. Maize straw at rates of 0 (CK ), 4 500, 9 000 and 13 500 kg/hm2 was placed on field plots. The results indicated that the average soil water storage in the 0–200 cm soil layers under the three different rates of straw mulch were 16.52, 25.52 and 34.04 mm, respectively, significantly (P<0.05) higher than that of CK, and the average field evapotranspiration (ET) in the 0–200 cm soil layers were 4.43, 8.23 and 6.96 mm, respectively, significantly (P<0.05) lower than that of CK during 0–60 days after sowing. Besides, the average grain yield and water use efficiency (WUE) of the treatment with 9 000 kg/hm2 of straw mulch were optimal among the treatments, its grain yield and WUE increased by 11.03% (P<0.05) and 9.25% (P<0.05) compared with the CK, while it was medium with the treatment of 13 000 kg/hm2, and lowest with the treatment with 4 500 kg/hm2. It is suggested that the treatment with 9 000 kg/hm2 of straw mulch is preferable for Weibei highland area in China, as the precipitation is below than 390 mm during the maize growing season.