Abstract: Vegetable is nitrophile and always accumulate NO3-. NO3- pollution in vegetables damages people’s health seriously, causing a great concern. Vegetable’s roots absorb NO3- mainly by the way of active absorption. Under retro-electrochemical gradient(170-250mv), NO3- is absorbed into the interior of root through symplast in a state of ion. NO3- is deoxidized into NO2- by nitrate reductase. The unharmonization of absorption, transportation and reduction of nitrate can bring about nitrate and nitrite accumulation excessively in vegetable. Nitrite accumulation can be affected by species and varieties of vegetables, fertilizer types and loading levels, and vegetable growth environments factors(light, temperature, water and CO2 ).