In this study, we examined the combined effects of irrigation and phosphorus supply on morphology and structure of special root hairs on nodal roots of Zhengmai 9023, a strong-gluten cultivar of wheat (Triticum aestivum L.). The experiments, conducted in the middle and late growing periods in 2009 and 2010, consisted of a 2 × 3 factorial experimental design with four replications. The effects of water supply on morphology of special root hairs were significant after jointing. Increased water supply was associated with significantly decreased length of special root hairs. Compared with those in the waterlogging treatment, the length and diameter of special root hairs from jointing to grain formation in optimal irrigation treatments (P<0.01). The diameter of special root hairs slightly increased before jointing, and thereafter the differences in diameter of special root hairs among the different water treatments gradually increased. There was a significantdifference in the diameter of special root hairs between the solely rain-fed treatment and the waterlogging treatment. The length and diameter of special root hairs increased with phosphorus supply (P<0.05). For special root hair length, there was a significant difference between the control (CK) and high phosphorus supply treatment in the solely rain-fed treatment, and an extremely significant difference between the CK and high phosphorus supply treatment in the waterlogging treatment. From jointing to grain formation, the difference in special root hair diameter between the CK and high phosphorus supply treatments was extremely significant. After grain formation, the diameter of special root hairs decreased significantly and the difference in diameter between the different water treatments was not significant. The length and diameter of special root hairs significantly increased with phosphorus supply at a fixed irrigation level, and significantly decreased with soil moisture content at a fixed phosphorus level. After jointing, in the rain-fed treatment coupled with high phosphorus supply, special root hairs were full with a complete structure, thickened cell walls, distinct nuclei, vacuoles, and mitochondria. In the low phosphorus supply treatment coupled with waterlogging, special root hairs were twisted and deformed with thin cell walls, diffuse nuclei, and indistinct plasma membranes and microbodies. These results indicate that maintaining soil moisture at appropriate levels and increasing phosphorus supply could increase the length and diameter of special root hairs on nodal roots and retain favorable cell morphology and structure in wheat.