French fry potato variety‘Kennebec’was fertilized at six nitrogen rates in a plot experiment, and the effects of different nitrogen rates on potato dry matter content were studied. The nitrate N concentration in petiole of potato was determined;function model between nitrate N concentration in petiole and dry matter content of French fry potato tuber was obtained. The results showed that with increasing of the nitrogen, the change of dry matter content of potato was a single-peak curve. The quadratic function was fitted to N rate and dry matter content of potato, forecasting that the tuber dry matter content of‘Kennebec’reached 20.6% of the maximum value when nitrogen rate was 122 kg/ha. The correlation of the nitrate N concentration in petiole and dry matter content in different periods reached significant level, and the corresponding quadratic function was obtained, with the optimal value of the nitrate N concentration in petiole being 2.45%, 2.20%, 2.06%, 1.74%, 1.51%, 1.34%, 1.08%, 0.87%and 0.66%for 10, 20, 30, 40, 50, 60, 70, 80 and 90 days after emergence, respectively. The equation of optimum value of the nitrate N concentration in petiole and days after emergence was y=-0.02 x+2.3123, R2=0.9949. The equation could be used to guide applicating nitrogen and achieve the goal of dry matter content control of potato.%以‘抗疫白’（Kennebec）为供试材料，设计6个氮肥梯度，通过田间小区试验，研究不同施氮量对马铃薯块茎干物质含量的影响，并测定植株叶柄的硝态氮含量，建立叶柄硝态氮含量与炸条型马铃薯块茎干物质含量函数模型。结果表明，马铃薯块茎干物质含量随着施氮量的增加表现为单峰曲线变化。对施氮量和马铃薯块茎干物质含量进行拟合二次函数方程，预测出‘抗疫白’在施氮量为122 kg/hm2时干物质含量达到了最大值20.6%。不同时期的叶柄硝态氮含量与块茎干物质含量相关性均达到了显著水平，并获得相对应的函数方程，计算得出获得最佳的干物质含量出苗第10,20,30,40,50,60,70,80和90 d叶柄硝态氮含量理论最佳值依次为2.45%，2.20%，2.06%，1.74%，1.51%，1.34%，1.08%，0.87%和0.66%，及叶柄硝态氮含量的最佳值与出苗后天数的拟合方程y=-0.02 x+2.3123，R2＝0.9949。可以利用该拟合方程，指导田间氮肥施用，达到控制块茎干物质含量的目的。
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