The genetic diversity of 255 mango germplasms in Nujiang Valley were investigated by comparing 24 morphological characters. The results showed that the mango germplasm have rich diversity in phenotypic traits, including single fruit weight, fruit length, seed weight, seed width, fruit shape, pericarp color, flesh color, aroma, taste, and maturity date. The wide variation were among the 11 quality characters of mango with variation efficient of 12.44%—56.44%, the largest coefficient of variation was single fruit weight while the smallest was leaf width. The Shannon-weaver index of 13 quantitative traits in mango was 0.68—2.21，the average diversity indexes was 1.42. The diversity index of the leaf texture was the lowest, while the flesh color were the highest. The thick pericarp, the small fruit，the big seed，the low edible rate , early maturity, sweet and sour , and the poor quality of morphological characters takes up a great proportion in 255 mango germplasms , which could be divided into 5 categories by cluster analysis. There existed significant genetic difference among the materials collected from different areas, and those collected from same area also showed significant genetic differentiation. Further more, 41 specific germplasm resources were initially selected based?on?identification and evaluation of phenotypic characters, which have characteristic?aroma,?off-season?blossom, stress resistance, early-maturing, small fruit, and high yield.