Abstract: Objective To systematically evaluate the relationship between body mass index (BMI) and hypertension risk in the elderly. Methods Systematic searches were conducted in databases, including China National Knowledge Infrastructure(CNKI), VIP Database, Wan Fang Database, PubMed, Web of Science, China Biology Medicine disc(CBM), Cochrane Library, and EMbase, with the search time frame spanning from January 2005 until May 2025. Two researchers independently performed literature screening, data extraction and quality assessment. RevMan 5.3 software was used to conduct a quantitative meta-analysis of published studies on the relationship between BMI and hypertension in the elderly, with the odds ratio (OR) and its 95% confidence interval (95% CI) as effect measures. Heterogeneity was assessed using the I² statistic and the Q test. A fixed-effects or random-effects model was selected based on the degree of heterogeneity to quantitatively pool the association between BMI and hypertension in the elderly population. Results A total of 28 studies involving 281 548 subjects were included. Meta-analysis results indicated that compared with normal weight, underweight was negatively correlated with the risk of hypertension in the elderly (OR=0.58, 95%CI: 0.49-0.69), while overweight (OR=1.62, 95%CI: 1.50-1.75) and obesity (OR=2.68, 95%CI: 2.38-3.00) were positively correlated with an elevated risk. Moreover, subgroup analysis revealed that the odds ratios (OR) for overweight and obese individuals calculated referring to WHO standards were significantly higher than those based on Chinese standards, with the risk increase being more pronounced in the obese subgroup. Conclusion High BMI is a important factor associate with hypertension in the elderly. However, the application of different BMI criteria leads to significant differences in risk estimation. For hypertension screening among the Chinese elderly population, adopting the domestic Chinese BMI criteria may be of greater public health significance.