Evaluation of the arsenic content in food has always been an important issue due to its high toxicity. This is especially relevant for Vietnam, a country with high arsenic contamination. The present study focuses on the development of a model function to predict As uptake in the vegetable Brassica perviridis as a function of the conditions of plant growth and soil parameters. The content of the As and Fe in the samples was determined by neutron activation analysis at the IBR-2 reactor; the soil pH and total organic carbon content were measured in the Institute of Nuclear Science and Technology –Vietnam Atomic Energy Institute (Hanoi, Vietnam). Obtained data have shown that As uptake in the Brassica perviridis plants grown in northern Vietnam could be presented as a function of soil parameters such as pH, organic carbon content, and Fe content, but is not dependent on As content in soil. Particularly high Fe content in Vietnamese soils contribute to As immobilization and prevent its uptake by plants. Regression Data Analysis was used to extract the model function with good corresponding statistics: correlation factor R > 0.97, the probability p-value of independent variable coefficients in the range from 1.86E-07 to 0.007, and the significance F of the model < 1.49E-11. The obtained values demonstrate the reliability and the trueness of the applied model at given soil characteristics and conditions of plants cultivation. The concertation of As in irrigating water could be regarded as the main source of the As uptake in plants and need to be investigated.