Abstract: Many scientists have paid great attention to the internal carcinogens for the last ten years. The typical examples of the predecessors of N-nitro compounds were nitrate and nitrite.lt has been confirmed by animal experiments that nitrate and nitrite,when absorbed by the human body from food, may result in a higher morbidity rate of cancers.In this study,Yangzhoag county, where the mortality rate of esophageal cancer were as high as 2.84‰,has been taken as a rest area,and Nanjing city as a check.’Nitrate and nitrite contents in several kinds of foods (including vegetables, grains, meat, fish drinking water etc.) were measured from the view point of food composition and the Value of the contents was compared with that of ADI stipulated by WHO/PAD. The results showed that the average NO^-₃, amount absorbed by human body in a season time in Yanzhong was 2.1-2.4 times more than the standard Value, and 1.63-1.67 times higher than in Nanjing. More than 9% of nitrate absorbed, came chiefly from fresh vegetables, 2-14% from pickles, 1-3>% from grain and meat as were as from drinking water. Moreover, among different vegetables, leaf vegetables contained the highest contents of nitrate, eggplant and fruit Vegetables contained the lowest. During winter and spring, when leaf Vegetables were prevalent in market, more nitrate was liable to be absorbed. The evaluation of food compositions,screening Vegetables with lower nitrate content, and to improve diet of people would be important measures lo decrease the morbidity rate of cancers.