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Cold stress usually causes the abscission of floral organs and a decline in fruit setting rate, seriously reducing tomato yield. Auxin is one of the key hormones that affects the abscission of plant floral organs; the <i>YUCCA</i> (<i>YUC</i>) family is a key gene in the auxin biosynthesis pathway, but there are few research reports on the abscission of tomato flower organs. This experiment found that, under low temperature stress, the expression of auxin synthesis genes increased in stamens but decreased in pistils. Low temperature treatment decreased pollen vigor and pollen germination rate. Low night temperature reduced the tomato fruit setting rate and led to parthenocarpy, and the treatment effect was most obvious in the early stage of tomato pollen development. The abscission rate of tomato pTRV-<i>Slfzy3</i> and pTRV-<i>Slfzy5</i> silenced plants was higher than that of the control, which is the key auxin synthesis gene affecting the abscission rate. The expression of <i>Solyc07g043580</i> was down-regulated after low night temperature treatment. <i>Solyc07g043580</i> encodes the bHLH-type transcription factor <i>SlPIF4</i>. It has been reported that <i>PIF4</i> regulates the expression of auxin synthesis and synthesis genes, and is a key protein in the interaction between low temperature stress and light in regulating plant development.