<p>Excess barium (Ba) in soil can result in Ba over-enrichment in crops, which may adversely affect human health. However, the transport and isotopic fractionation of Ba in plants remain poorly understood. We analyzed the Ba content and isotopic composition of three crops (rice, pak choi, and maize) grown in Ba-contaminated soil. Results for rice and maize demonstrated significant fractionation and environmental sensitivity in the transport of Ba, and longer flooding durations were found to increase Ba accumulation in rice grains during the filling stage. In contrast, research on pak choi revealed limited fractionation and strong uptake and transport of Ba. The estimated daily intake of Ba in the edible portion of pak choi (stems and leaves) was 15–24 times the recommended daily intake of 0.2&#xa0;mg/kg body weight per day. Therefore, pak choi was the least suitable crop for Ba-contaminated areas. This study provides new insights into how Ba isotopic fractionation can trace Ba transport in crops, offering practical applications for food safety and environmental monitoring.</p> Graphical abstract <p></p>