Inflorescence type is one of the important ornamental traits of Hydrangea macrophylla. To localize the key genes controlling inflorescence types， 125 H. macrophylla individual plants were re-sequenced to obtain the single nucleotide polymorphisms （SNPs）. Genome-wide association study （GWAS） was carried out using general linear model （GLM） and mixed linear model （MLM） of Fastlmm and GEMMA software， to identify the SNPs that strongly associated with inflorescence types. respectively. 285 SNPs significantly associating with floral phenotypes were found （cutoff： -log₁₀（P）>9）， which contributed to the phenotypic variation from 11.80% to 60.54%. Twelve SNPs from 285 loci were further genotyped by Sanger sequencing and kompetitive allele-specific PCR （KASP） in 52 hydrangea cultivars， and 9 hybrid populations. Four SNPs including Hma1.2p1_0060F.1_796640， Hma1.2p1_0060F.1_1540773， Hma1.2p1_0653F.1_868484 and Hma1.2p1_0669F.1_949341 were validated closely associating with inflorescence type， which indicated that the genes controlling hydrangea inflorescence type were probably allocated in three Scaffolds Hma1.2p1_0060F.1， Hma1.2p1_0653F.1 and Hma1.2p1_0669F.1. According to the DNA sequence surrounding the 285 SNPs associating with floral phenotypes， a total of 1287 genes were annotated. In these genes， four genes putatively encoding for transcription factors， including two MYBs， one MADS， and one bHLH， were predicted to be associated with hydrangea inflorescence type. These findings provided a foundation for future gene cloning and molecular marker-assisted breeding for hydrangea.