Hereditary multiple exostose(EXT) is an autosomal dominant disorder of skeletal system. Three genetic loci have been identified at 8q24.1(EXT1), 11p11(EXT2) and 19p(EXT3) respectively. In this paper, EXT2 gene was cloned with positional cloning and homologous screening. SSCP and sequencing analysis have been done in 37 EXT patients who came from 20 EXT families, 2 mutations of insertion were tested in 2 patients. This confirmed that the gene cloned in this paper was EXT2 gene which locus at 11p11. Additionally EXT4 gene was cloned with homologous screening and located at 1p36.1 with FISH in this paper.