This study evaluated the level of genetic diversity in 92 accessions of cucumber (Cucumis sativus L.) core germplasm using seedling and early flowering stage morphological markers. The results showed there were significant genetic variations in the seedling and early flowering stage traits of the tested cucumber core germplasm. The average variation coefficient between each germplasm traits was 31.0%. The variation coefficients for the node of the first female flower with 59.4% and the date of flowering with 14.2% were the biggest and the smallest, respectively. Based on the morphological traits, cluster analysis indicated the 92 accessions could be divided into three and eight groups at the Pearson correlation coefficient of 6.5 and 3.5, respectively. The results of the present study enrich the evaluation system and provide important information for the exploitation and utilization of excellent gene resources of melons.