It is important to promote adaptability of maize varieties to high-density, low nitrogen and drought stresses so as to improve maize yield. Six maize varieties of Yuyu 22, Shaandan 902, Jingdan 28, Shaandan 8806, Xianyu 335 and Zhengdan 958 were planted under two kinds of densities (45 000 and 75 000 plants ha^-1), pure nitrogen levels (112.5 and 337.5 kg ha^-1) and water treatments (controlling water at prophase and normal irrigation) in fields to elucidate effects of stresses (high density, low nitrogen and drought) on yield formation of maize varieties. Main physiological parameters of source-sink characters The results showed that differences of grain yield were little among maize varieties under less environmental pressure (low density, high nitrogen and normal irrigation), while these were significant under stress (high density, low nitrogen and drought). Changes of source characters (LAI, P_n of ear leaves and source capacity), sink characters (sink capacity of population), harmonious source-sink characters (sink-source ratiograin yield. There were significantly positive correlations between grain yield and LAI, source capacity, dry matter accumulation at maturity, dry matter accumulation from silking stage to maturity, sink capacity of population and HI. To improve maize yield, we should strengthen artificial selection for adapting to natural selection, improve source-sink characters of maize population under stress, enhance leaf photosynthetic efficiency from silking stage to maturity, strengthen source and promote sink, and improve production capacity and adaptability under stresses., grain filling rate and HI), dry matter accumulation at maturity and dry matter accumulation from silking stage to maturity showed the same rules as and grain yield were measured.