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<i>Lilium</i> is one of the most widely cultivated ornamental bulbous plants in the world. Although research has shown that variable temperature treatments can accelerate the development process from vegetative to reproductive growth in <i>Lilium</i>, the molecular regulation mechanisms of this development are not clear. In this study, <i>Lbr</i>-miR171b and its target gene, <i>LbrSCL6</i>, were selected and validated using transgenic functional verification, subcellular localization, and transcriptional activation. This study also investigated the differential expression of <i>Lbr</i>-miR171b and <i>LbrSCL6</i> in two temperature treatment groups (25 °C and 15 °C). <i>Lbr</i>-miR171b expression significantly increased after the temperature change, whereas that of <i>LbrSCL6</i> exhibited the opposite trend. Through in situ hybridization experiments facilitated by the design of hybridization probes targeting <i>LbrSCL6</i>, a reduction in <i>LbrSCL6</i> expression was detected following variable temperature treatment at 15 °C. The transgenic overexpression of <i>Lbr</i>-miR171b in plants promoted the phase transition, while <i>LbrSCL6</i> overexpression induced a delay in the phase transition. In addition, LbrWOX4 interacted with LbrSCL6 in yeast two-hybrid and bimolecular fluorescence complementation assays. In conclusion, these results explain the molecular regulatory mechanisms governing the phase transition in <i>Lilium</i>.