The corpus luteum is the principal progesterone-secreting gland, while primary cilia function as pivotal organelles in intercellular signal transduction. Together, they play an essential role in the establishment and maintenance of pregnancy. However, the mechanisms underlying the role of primary cilia in granulosa cell luteinization in mouse ovaries remain poorly understood. This study discovered the regularity of primary cilia in mouse ovaries and revealed the role of primary cilia in regulating progesterone synthesis in luteinized granulosa cells. In vivo test results showed that the expression of primary cilia was obvious in the corpus luteum. The secretion of P4 in mice was significantly increased at 6, 12, 24, 48, and 72 h. The secretion of P4 and the expressions of luteinization markers (STAR, 3β-HSD) and primary ciliate proteins (IFT88, Arl13B) were significantly up-regulated at different time points (6, 12, 24 h and 24, 48, 72 h), and the INS group was significantly higher than the LH group and the control. In vitro test results showed that the follicular granulosa cells were luteinized under INS, the length and number of primary cilia increased, and the secretion of progesterone increased. The expression levels of STAR and 3β-HSD of the primary cilia marker Arl13B and luteinization markers were increased, while the expression levels of CYP19A1 were decreased. Ciliobrevin A (CBA) and Y-27632 2HCl were used to regulate the expression of primary cilia. The results showed that after CBA treatment, the expression level of cilia protein Arl13B decreased, and the secretion level of P4 and the expression levels of STAR and 3β-HSD decreased, indicating that the level of luteinization decreased. Conversely, after inducing ciliogenesis with Y-27632 2HCl, the results were the opposite of those observed with CBA treatment. In conclusion, our study demonstrates that primary cilia regulate the expression of steroidogenic enzymes, thereby promoting progesterone secretion by granulosa cells in mice and ensuring proper luteinization.