Abstract: Abstract: Years of small power machincal shallow rotary tillage often causes issues such as shallow top soil layer and thick plough pan in the root layer. Subsoiling is an effective mean to solve the those issues. In this study, effect of subsoiling on root morphological and physiological characteristics of spring maize was investigated in order to understand the mechanism behind the high-yield cultivation of spring maize. In a two-year field experiment (2012 and 2013), two maize varieties of Zhengdan958 and Xianyu335 were planted in soils tilled with different practices including rotary tillage and subsoiling plus rotary tillage. The results showed that subsoiling could significantly (P<0.05) or extremely significantly (P<0.01) increase the maize yield. In the milking and maturity stages, subsoiling also significantly (Xianyu335, P<0.05) or extremely significantly (Zhengdan958, P<0.01) increased the dry root weight of spring maize, especially in soils under 40 cm depth. The root range of inter plant and inter row of two spring maize varieties at the 30 cm soil layer was significantly (P<0.05) higher in the subsoiling plus rotary tillage treatment than in the rotary tillage treatment. In addition, subsoiling increased the root number of per plant and the specific root length. The root activity of spring maize in milking stage in the soil layers below 60 cm was significantly higher in the subsoiling treatment than the rotary tillage treatment, and the difference between both treatments was increased along the depth of the soil. The activities of superoxide dismutase (SOD) and peroxidase (POD) in the treatment of subsoiling+rotary tillage treatment were higher than that of rotary tillage in silking stage under the soil layers below 40 cm. But the malondialdehyde (MDA) content was lower in the former than the latter treatment. Therefore, subsoiling promoted root development, especially increased root dry weight at the deep soil layer and root distribution along the soil profile, and kept high physiological activity, thus resulting in high yield of spring maize.