Local melon germplasm in Xinjiang is the most important resources for hami-melon genetic improvement because of its abundant genetic diversity. By combining source grouping and systematic cluster selection, an optimal sampling scale was determined after multiple comparisons of 29 phenotypic traits of the 121 melon landraces (Cucumis melo L.) in Xinjiang, and 25 landraces were selected as preliminary core collection then. Supplemented 5 landraces with elite, rare and extreme traits by hand, the core collection of total landraces was conformed, and the sampling scale was about 25% lastly. 7 parameters, such as ratio of phenotype retained, genetic diversity, coefficient of variance, variance of phenotypic frequency, and conformity of extreme difference, average and standard deviation were examined between preliminary and confirmed core collection, core collection and total landraces. The results showed that except conformity of standard deviation all parameters of confirmed core collection were more suitable than or the same as that of preliminary one, and representation of confirmed core collection was better than that of the preliminary one. The genetic diversity and variation in the core collection obtained were well presented in the total landraces.