The influence factors affecting the accuracy of the determination of nitrogen in the coal such as coal sample,weighing accuracy ,and decomposition of the hard coal samples, the influence of nitrogen in coal on blank value data were analyzed,the corresponding solutions were put forward , the experiment of the hard coal samples were studied. It was concluded that reducing the dosage of sample couldn't achieve the goal of reducing the test dose, the test conditions at blank with sucrose were more close to the test conditions of determination of nitrogen in the coal.