The rice processing chain is an extremely important part of the rice supply chain, so the risk assessment on the main pollutants in the rice processing chain is of great significance. The existing risk assessment methods are subjective on the weight determination of risk indicators and the comprehensive risk assessment of the processing chain, and they do not consider the characteristics of the indicators, resulting in the unreasonable assessment results. And the existing assessment models have poor robustness and low accuracy. To solve these problems, this article proposes a risk assessment method for the entire rice processing chain based on Kmeans + + and extreme learning machine (ELM). Based on multi-level risk assessment index system, a risk assessment model of main pollutants in rice processing chain was constructed. According to the characteristics of rice pollutants, the pollutant index toxicological characteristics were integrated into the entropy weight. The comprehensive risk index of the processing chain was obtained, and the Kmeans + + clustering algorithm was used to cluster the index and adaptively mining data characteristics to classify risk levels. ELM was used for risk assessment. The proposed method was validated by 75 sets of rice processing chain data, based on six pollutant indicators of Pb, Cd, Hg, aflatoxin B1, zearalenone and deoxynivalenol. The results show that the risk classification accuracy of the proposed method in the test set was 93.3%, and it was more accurately and reasonably than the compared methods. This study strengthens the advantages of big data and artificial intelligence technology in food safety and supervision in the process of digital transformation of agriculture, provides more accurate and reliable decision-making basis for food safety supervisory departments, and lays a solid foundation for subsequent rapid warning and prevention and control decisions.