Based on research of 36 patients with hypertrophic cardiomyopathy, 44 patients with dilated cardiomyopathy and 72 normal controls, 5-flanking region of NPPB (Natriuretic Peptide Precursor B) gene was applied bypolymerase chain reaction (PCR), the polymorphism of NPPB gene was analysis by direct sequencing.Then make preliminary statistical analysis according to different genotypes.Among 36 patients with hypertrophic cardiomyopathy, there arc 20 patients with genotype of c.-1335 A/A + c.-1343 A/A, 12 patients with genotype of c.-1298 G/T, 8 with c.-1298 T/T; while there are 18 patients with geno type of c.-1298 G/T, 3 with genotype of-1298 T/T among the group with dilated cardiomyopathy; at the same time, there are 2 people with genotype of c.-1335 A/A + c.-1343 A/A, 17 with c.-1298 G/T genotype, and 8 with c.-1298 T/T genotypein normal controls.The incidence of hypertrophic cardiomyopathy of people with e.-1298 T genotype is 5,14 times that of people with G genotype, while the incidence of dilated cardiomyopathy is about 3 times.Compared with people with genotypes of c.-1335 T/T + c.-1343 T/T, the incidence of hypertrophic cardiomyopathy of people with genotypes of c.-1335 A/A + c.-1343 A/A will increase by nearly 3.3 times.That is the changes of CTIT repeat sequence polymorphism of the NPPB gene s 5-flanking region may be related to hypertrophic cardiomyopathy and dilated cardiomyopathy, and c.-1335 A/A + c.-1343 A/A is a novel found polymorphism.