Northeast China is a key area for maize production, but the low temperatures often result in delayed maize growth and slow maturity, as well as low grain quality and high grain moisture. So, to help improve maize yield, we studied the effects of PASP-KT-NAA on maize leaf nitrogen assimilation characteristics after florescence over different accumulated temperature regions with Zhengdan 958 and Fengdan 3 maize seeds as materials, in Heilongjiang province. The protein content in maize leaves is low and the key enzyme activities of nitrogen metabolism are susceptible to changes in environment, such as frost harm, etc. For this reason, the effects of different temperatures and the PASP-KT-NAA mixture on maize NRA (nitrogen reductive activity) in leaf tissue has been studied in three different accumulated temperature zones in Heilongjiang province, during 2010-2011. In field experiments, the first zone trial plot is located in the science station of Heilongjiang academy of agriculture sciences in Harbin. Its general accumulated temperature is ≥2800℃, but the accumulated temperature in the maize growing season in 2010 and 2011 is 3154.2℃ and 3004.2℃, respectively. The second zone trial plot is located in the science station of Heilongjiang Academy of Agricultural Sciences in Suihua City. Its general accumulated temperature is ≥2600℃, but the accumulated temperature in the maize growing season in 2010 and 2011 is 2901.8℃ and 2885.0℃, respectively. The third zone trial plot is located in Yi'an County. Its general accumulated temperature is ≥2400℃, but the accumulated temperature in the maize growing season in 2010 and 2011 is 2728.3℃ and 2602.6℃, respectively. The results showed that: (1) The NRA, NO₃^- content, leaf nitrogen content and chlorophyll content were affected by temperature, in zone order of I > Ⅱ > Ⅲ. After PKN treatment, FDTR and ZDTR ear leaf NRA in the three accumulated temperature zone were significantly higher than that in the water control and leaf nitrogen content and chlorophyll content was higher than the water control. The average of the ear leaf free amino acid of the two maize varieties performed "up-down" trends with the growth process, and reached its maximum 20 d after florescence. The soluble protein of zone Ⅰ tended to decrease with the growth process, with zones Ⅱ, and Ⅲ firstly increasing then decreasing with the growth process, reaching its maximum at 10 d after florescence. After PKN treatment, ear leaf free amino acid and soluble protein in samples from zone Ⅰ, Ⅱ and Ⅲ were significantly higher than the water control; (2) The grain yield of zone Ⅰ was higher than that for zone Ⅱ and Ⅲ. PKN treatment raised grain yield higher than those of the water control. The increased rate of ZDTR yield in zones Ⅰ, Ⅱ and Ⅲ in 2010 and 2011 were 3.09%-8.81%, 4.61%-10.91%, 5.91%-13.51%, respectively. The increased rate of FDTR yield in zones Ⅰ, Ⅱ and Ⅲ, in 2010 and 2011 were 2.43%-5.19%, 3.03%-6.01%, 2.57%-4.62%, respectively. PKN treatment improved the maize ear leaf nitrogen assimilation key enzyme activity and its product content over different accumulated temperature regions, promoted nitrogen assimilation normally under low temperature conditions and eventually increased yield.