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Reducing fat deposition in sheep (<i>Ovis aries</i>) tails is one of the most important ways to combat rising costs and control consumer preference. Our previous studies have shown that oar-miR-432 is differentially expressed in the tail adipose tissue of Hu (a fat-tailed sheep breed) and Tibetan (a thin-tailed sheep breed) sheep and is a key factor in the negative regulation of fat deposition through <i>BMP2</i> in ovine preadipocytes. This study investigated the effect of oar-miR-432 and its target genes in ovine preadipocytes. A dual luciferase assay revealed that <i>DDI1</i> is a direct target gene of oar-miR-432. We transfected an oar-miR-432 mimic and inhibitor into preadipocytes to analyze the expression of target genes. Overexpression of oar-miR-432 inhibits <i>DDI1</i> expression, whereas inhibition showed the opposite results. Compared with thin-tailed sheep, <i>DDI1</i> was highly expressed in the fat-tailed sheep at the mRNA and protein levels. Furthermore, we transfected the overexpression and knockdown target genes into preadipocytes to analyze their influence after inducing differentiation. Knockdown of <i>DDI1</i> induced ovine preadipocyte differentiation into adipocytes but suppressed oar-miR-432 expression. Conversely, the overexpression of <i>DDI1</i> significantly inhibited differentiation but promoted oar-miR-432 expression. <i>DDI1</i> overexpression also decreased the content of triglycerides. Additionally, <i>DDI1</i> is a nested gene in intron 1 of <i>PDGFD</i>. When <i>DDI1</i> was overexpressed, the <i>PDGFD</i> expression also increased, whereas <i>DDI1</i> knockdown showed the opposite results. This is the first study to reveal the biological mechanisms by which oar-miR-432 inhibits preadipocytes through <i>DDI1</i> and provides insight into the molecular regulatory mechanisms of <i>DDI1</i> in ovine preadipocytes. These results have important applications in animal breeding and obesity-related human diseases.