Abstract: The dynamics of soil available nitrogen (SAN) and total nitrogen (STN) in spring wheat fields following two years (2003 and 2004) of regulated deficit irrigation (RDI) was studied in Hexi oasis irrigation region. The differences in soil nitrogen index at harvest (between the two experimental years) were analyzed using Paired-Sample T-Test (2-tailed), and regression relations between SAN,STN and total irrigation water (IR) for the entire wheat growing season developed. The regression relations provided relevant hints for analyzing the effects of RDI on soil nitrogen in spring wheat fields. Results show that RDI significantly affect soil nitrogen in the 0 ~ 20 cm, 20 ~ 40 cm and 0 ~ 40 cm soil layers in spring wheat fields for 2003 and 2004, while Paired-Sample T-Test on soil nitrogen at wheat harvest indicates that STN and SAN in the 0 ~ 20 cm soil layer, STN in the 20 ~ 40 cm and 0 ~ 40 cm soil layers in 2004 are significantly higher than in 2003. However, no significant difference exists in SAN in the 20 ~ 40 cm and 0 ~ 40 cm soil layers for 2003 and 2004. Furthermore, STN in the 0 ~ 40 cm soil layer has a negative linear correlation with IR during wheat growing seasons, while SAN has a positive linear correlation with IR.