Abstract: A linkage map of cucumber was constructed using 152 progenies of F2 generation derived from a cross between the low light stress tolerance line M22 and the low light sensitivity line M14 in the experiment. The effects of low light stress on the hypocotyl traits of cucumber were investigated in a set of 123 F2:3 lines in the seeding stage in the autumn of 2008 and spring of 2009. QTL analysis was undertaken on the basis of a genetic linkage map of the corresponding F2 population that was constructed using composite interval mapping. F2:3–based QTL analysis of the hypocotyl length and hypocotyl thick in the two environments revealed 15 QTLs were located in five linkage groups，i.e.，the 1st，2nd，4th，6th，and 7th，each accounted for 5.5%–19.8% of the phenotypic variation. In the autumn of 2008，the total phenotypic variation among the F2:3 lines accounted for by the QTLs for hypocotyl length and hypocotyl thick were 52.8% and 27.7%，respectively. In the spring of 2009，7 QTLs were identified，the total phenotypic variation were 34.6% and 34.7%，respectively.

Key words: cucumber, Cucumis sativus L., low light stress, hypocotyl, QTL analysis