Brassica rapa accessions need vernalization (the induction of flowering by exposure to the prolonged cold of winter) except for a few early flowering accessions. In B. rapa vegetables such as Chinese cabbages, turnips, and pak choi, premature bolting results in reduced quality and yield. Thus, high bolting resistance is a desirable trait for B. rapa vegetable breeding. Our study found that several B. rapa accessions were extremely late-flowering and did not flower even when exposed to more than six weeks of cold treatment. To identify the gene responsible for this high bolting resistance, we performed QTL-seq analysis using the F2 population derived from a crossing between the extremely late-flowering accession and the common late-bolting Chinese cabbage cultivar. The distribution of flowering time in the F2 population suggested that high bolting resistance could be explained by recessive mutations in two factors. In addition, QTL-seq allowed us to identify several QTLs. Although the detected QTLs did not overlap with the region covering FLOWERLING LOCUS C (FLC), a key gene for vernalization, flowering-related genes such as VERNALIZATION INSENSITIVE 3 (VIN3) were found on these QTLs. We also performed RNA-seq with and without prolonged cold treatments in accessions of B. rapa including this high bolting resistant accession. We are integrating QTL-seq and RNA-seq data to screen candidate genes for high bolting resistance.