Specific leaf area (SLA), the ratio of green leaf area to its dry weight, is one of the most important parameters of leaf function evaluation, which could reflect resource utilization ability and adaptability to different environments of plants. Recently, many preliminary conclusions have been reported about the variation trend of maize SLA under drought stress, but most of them were qualitative descriptions and lacked quantitative analysis. In this study, based on water-control field experiments in Hebei Gucheng, China from 2013 to 2015, the variation trends of summer maize SLA on major developmental stages were investigated, and the quantitative relationships between SLA and soil moisture on different developmental stages were also established. As the experiment designed, 3 major developmental stages of summer maize (emergence to jointing, jointing to tasseling, tasseling to maturity), as well as[(emergence to jointing) + (jointing to tasseling)],[(emergence to jointing) + (tasseling to maturity)], and[(jointing to tasseling) + (tasseling to maturity)], were all water controlled in turn. The experiment was set with 4 water-control treatments and 1 contrast treatment, in which the soil relative moisture θ was ≤ 40% (T1), 40%-60% (T2), 60%-80% (T3), >80% (T4), and natural precipitation (T5), respectively. Results showed that the summer maize SLA presented a declining trend during the entire growing season, with an averaged variation range of 14.6-34.9m²/kg. Specifically, the SLA reached maximum value at seven-leaf stage (34.9m²/kg), declined rapidly at jointing stage (23.4m²/kg), decreased slightly at the tasseling stage (18.1-18.8m²/kg), and was the lowest at the maturity stage with an average of 14.6m²/kg. Experimental data showed that drought stress could significantly decrease the leaf area and dry weight of summer maize, but the SLA showed a "compensatory" larger value in order to compensate for the leaf expansion fatigue caused by insufficient photosynthates. The summer maize SLA had a significant linear negative correlation with soil moisture from the emergence to jointing and tasseling to maturity stages, with increase of 0.45m²/kg (emergence to jointing stage) and 0.07m²/kg (tasseling to maturity stage) when the soil relative moisture decreased by 1%, indicating that the summer maize had more adaptation to drought during emergence to jointing stage. However, the relationship between SLA and soil moisture on the jointing to tasseling stage was more complex; it first increased and then decreased with a parabola shape.