Loose-curd cauliflower is currently the main type of cauliflower consumed in China. Clubroot and black spot diseases are improtant diseases that directly and adversely affect the yield and quality of cauliflower. Therefore, to select varieties of good commercial quality with high and multiple resistance is one of the major goals in cauliflower breeding. In this study, we for the first time established the evaluation system of curd traits for loose-curd cauliflower germplasm resources. Sixty-six accessions of loose-curd cauliflower inbred lines were evaluated for eight characters of curd compactness, curd shape, surface smoothness, surface color, buds size, length of secondary lateral branch, pedicel color and curd hairiness. Each character was assigned a value for statistics and comparison. Eleven inbred lines were selected for excellent traits based on the evaluation system. With artificial inoculation at seedling stage, we identified and evaluated the resistance to clubroot and black spot of loose-curd cauliflower respectively. The results showed that none of the accessions were immune to clubroot, with 2 of high resistance, 9 of fair resistance, 16 of medium resistance, and none of the accessions were immune or highly resistant to black spot, with 4 of fair resistance, 10 of medium resistance. Only a few accessions were found to have dual resistance to clubroot and black spot diseases. Among them, ‘GY-40’ showed relatively high resistance to both diseases, ‘GY-21’ showed fair resistance to clubroot and medium resistance to black spot, and ‘GY-21’ showed medium resistance to both diseases. ‘GY-40’ is therefore an ideal parent line for breeding cauliflower varieties, due to its excellent traits and relatively high dual resistance to both clubroot and black spot diseases. The study will provide reference for evaluating curd traits of cauliflower germplasm resources, be of great significance for standardization of resources collection, sorting and preservation, and provide excellent accessions for breeding of loose-curd cauliflower varieties with dual resistance to clubroot and black spot diseases.