Abstract: Objective To investigate the effects of an insertion/deletion (I/D) polymorphism at the intron 16 of the gene of angiotensin converting enzyme (ACE) on the changes of serum lipid ratios and blood pressure induced by a high-carbohydrate and low-fat (HC/LF) diet in healthy Chinese Han youth. Methods Fifty six healthy Chinese Han young volunteers were enrolled. A washout diet was given for seven days followed by the HC/LF diet for six days. Serum lipids and blood pressure were measured on the 1^st, 8^th, and 14^th days. Serum lipid ratios were calculated. The ACE I/D polymorphism was detected by PCR. Results There were no significant differences of serum lipid ratios and blood pressure at baseline and before and after the HC/LF diet between theⅡ genotype and the D carriers (ID and DD genotypes) in the whole study population, the males or the females separately. When compared with those before the HC/LF diet, all the subjects regardless of the genotype experienced statistical decreases of low density lipoprotein-cholesterol/high density lipoprotein-cholesterol (LDL-C/HDL-C) and total cholesterol (TC)/HDL-C, but significant decrease of systolic blood pressure (SBP) was only found in the subjects with theⅡ genotype. After taking into account gender, triglyceride (TG)/HDL-C and Log (TG/HDL-C) decreased in the males with theⅡ genotype and increased in the female counterparts. The decreases of TC/HDL-C and LDL-C/HDL-C were observed in all the males and the female D carriers. SBP decreased only in the male D carriers. Conclusion The interaction of the HC/LF diet with the I allele of the intron 16 I/D polymorphism at the ACE gene decreases TG/HDL-C and log (TG/HDL-C) in males, but increases TG/HDL-C and log (TG/HDL-C) in females in the Chinese young population. The interplay with the D allele lowers SBP in males, and TC/HDL-C and LDL-C/HDL-C in females.