To study the function of rice pectin methyltransferase OsTSD2 genes and its effects on growth and development,a dwarf mutant was found by screening the mutants and experimentally verified. The T-DNA was inserted in the seventh intron of the gene OsTSD2. This mutant was named as tsd2a (tumorous shoot development 2a). Other two allelic mutants tsd2b and tsd2c were found as well. Three allelic mutants had lower seed setting percentage,shorter grain length,narrowed grain width and reduced 1 000-grain weight. The glume of mutant had darkened colors,aggravating the degree of rupture,new and seriously broken backside. Results of fluorescence immunoassay indicated that the declined germination rate of mutant seed was due to lower methylation pectin in scutellum of germinating mutant seeds. Defective function of pectin methyltransferase OsTSD2 gene may obviously make the defective development and germination of the rice seeds.