Background: With rapid economic development and lifestyle changes, diet-related diseases have become a major public health concern globally. China is experiencing significant dietary transitions. From 2001 to 2021, the intake of staple foods declined, while the consumption of animal-based foods and ultra-processed foods increased significantly. But comprehensive assessments of major dietary risk factors and the long-term health impacts of shifting dietary patterns in China remains unclear. Objective: This study aims to assess the disease burden attributable to dietary risk factors in China using data from the Global Burden of Diseases, Injuries, and Risk Factors Study 2021 (GBD 2021), and to examine long-term trends over the past three decades. Additionally, it provides an in-depth analysis of the three major diet-related disease categories in China: cardiovascular diseases, neoplasms, and diabetes and kidney diseases.v Methods: We extracted data from GBD 2021, focusing on diet-related health outcomes in China across 33 provinces/ regions. Measures included deaths, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life years (DALYs), stratified by age, sex, and region. Age-standardized rates (ASRs) were calculated, and temporal trends were analyzed using estimated annual percentage change (EAPC). Results: In 2021, dietary risk factors accounted for 1.70 million deaths and 38.39 million DALYs among Chinese adults aged 25 and above. The leading contributors were high sodium intake, low fruit consumption, and low whole grain intake. Cardiovascular diseases were the largest contributors to diet-related DALYs. The burden was more pronounced in males than in females, and highest among older adults aged 80 and above. Substantial regional variation was observed, with northeastern and western regions showing higher burden. From 1990 to 2021, overall disease burden due to dietary risks declined steadily, as reflected by decreasing ASR-DALYs (EAPC = -1.76), YLLs, and death rates. In contrast, YLDs showed a slight upward trend (EAPC = 0.75), indicating a shift toward increased years lived with disability. Additionally, the relative contributions of specific dietary risk factors changed considerably. Low vegetable intake, once ranked the third in 1990, dropped to the 12th by 2021, while high red meat consumption rose from the 15th to 7th place. Although the ranking of high-sugar beverage consumption did not change, the ASR- DALYs rate increased significantly, with a percentage change of 689.14% between 1990 and 2021. Conclusions: In China, the burden of diet-related diseases remains substantial. While the overall age-standardized disease burden has declined, marked regional and demographic disparities persist. Certain dietary risks, such as high red meat and sugar-sweetened beverage consumption are rising, and high sodium intake remains a serious concern. These trends highlight the urgent need for comprehensive, adaptable and evidence-based nutrition policies to be implemented, to address the evolving diet-related disease burden across diverse populations in China.