After model debugging, we designed a series of fertilizer andirrigation conditions as follows: N1, N2, N3, N4 and N5 mean the dose of pure nitrogen of 100, 200, 300, 400 and 500 kg/ hm², respectively; M0, M1, M2 and M3 represent the amount of organic fertilizer of 0, 7 500, 15 000 and 22 500 kg/ hm², respectively; I0represents no irrigation, Ib, Ik and Ig mean 50 mm water irrigated at the jointing stage, flowering period and grain-filling stage of Zea mays, respectively. Then the DSSAT model was used to simulate the growth situation of Z. mays with different water-fertilizer regimes under the conditions of light, temperature and rainfall in 2005. The results show that: 1) In the rain-fed conditions (no irrigation during the growth of Z. mays with the water depending on rainfall) with limited amount of N, the yield loss caused by the lack of N can be compensated by increasing the use of organic fertilizer; 2) Under the conditions of M1N4 treatment (the amounts of organic fertilizer and pure nitrogen were 7 500 and 400 kg/ hm², respectively) and M2N3 treatment (the amounts of organic fertilizer and pure nitrogen were 15 000 and 300 kg/ hm², respectively), no significant variations were observed in the yield of Z. mays: that of the former treatment was 14 313 kg/ hm² and that of the latter 14 711 kg/ hm², biomass of the former was 24 803 kg/ hm² and the latter 24 349 kg/ hm², yield productivities of N of the former was 40.8 kg/ kg and the latter 41.1 kg/ kg, and dry matter productivity of N of the former was 70.7 kg/ kg and the latter 70.4 kg/ kg. And all of them were at a high level. 3) Under the situation of simulated irrigation with a small amount of fertilizer, irrigation had little effect on Z. mays yield, indicating that the yield-limiting factor in this case may be fertilizer; when treated with a large amount of fertilizer, irrigation increased yield obviously, which is of important significance for productivity by ensuring water supply at the grain-filling stage.