The existence form of nitrogen in the coal and its measurement principle were expounded,the semi-micro Kelvin method experiment were analyzed.In the experiment,the coal samples under the boiling sulfuric acid catalyst could make the organics in coal be oxidized to carbon dioxide and water, etc., most of nitrogen be became ammonia;the excess sodium hydroxide was joined,and be absorbed by the boric acid solution;finally the nitrogen content in coal was measured with acid titration.The corresponding experimental conditions were studied, the several factors that affected the test results are accuracy were discussed.