The endosperm phenotype and the content of protein and starch were changed in the maize of opaque2(o2) mutant, its nutritional quality was greatly improved. We produced a pair of near-isogenic lines of o2 mutation which were constructed by backcrossing. Scanning electron microscopy and transmission electron microscopy were used to analysis the mature and developing endosperm. It was found that starch granules were arranged more random and loosely, and the protein bodies are smaller in CAL58/o2 compared with wild genotype. After analysis of nutrients between the two lines, we found that because of o2 mutation the content of lysine significantly increased 55.88%, total amino acid decreased 9.79%, total protein decreased 8.86%, and the content of fatty and starch increased 30.96% and 5.87% respectively. We also compared the differences of zein between the two lines and found that α、β-zein were decreased, γ-zein was increased in CAL58/o2.