Blood pressure-to-height ratio (BPHR) has been reported to perform well for identifying hypertension (HTN) in adolescents but not in young children. Our study was aimed to evaluate the performance of BPHR and modified BPHR (MBPHR) for screening HTN in children. A total of 5268 Chinese children (boys: 53.1%) aged 6-12 years and 5024 American children (boys: 48.1%) aged 8-12 years were included in the present study. BPHR was calculated as BP/height (mmHg/cm). MBPHR7 was calculated as BP/(height + 7*(13-age)). MBPHR3 was calculated as BP/(height + 3*(13-age)). We used receiver-operating characteristic curve analysis to assess the performance of the three ratios for identifying HTN in children as compared to the 2017 U.S. clinical guideline as the "gold standard". The prevalence of HTN in Chinese and American children was 9.4% and 5.4%, respectively, based on the 2017 U.S. guideline. The AUC was larger for MBPHR3 than BPHR and MBPHR7. All three ratios had optimal negative predictive value (~100%). The positive predictive value (PPV) was higher for MBPHR3 than BPHR in both Chinese (43.9% vs. 37.9%) and American (39.1% vs. 26.3%) children. In contrast, the PPV was higher for MBPHR7 than BPHR in Chinese children (47.4% vs. 37.9%) but not in American children (24.8% vs. 26.3%). In summary, MBPHR3 overall performed better than MBPHR7 and BPHR for identifying HTN in children. However, the three ratios had low PPV (<50%) as compared to the 2017 U.S. guidelines, which makes these ratios of limited use for HTN screening in children.