Aim To investigate whether CD137-CD137L signal through tumor necrosis factor receptor-associated factor-6/c-Jun amino-terminal kinase/activated protein-1 (TRAF6/JNK/AP-1) pathway to regulate the expression of nuclear factor of activated T cell c1 (NFATc1) in mouse vascular smooth muscle cell (VSMC). Methods Mouse primary VSMCs were cultured from aortic tissue block, and third to fifth generations of cells were used for the experiment. VSMCs were divided into 6 groups:control group, CD137 stimulation group, CD137 inhibition group, siTRAF6 intervention group, siJNK intervention group and siAP-1 intervention group. The expression levels of TRAF6, phosphorylated JNK (p-JNK), phosphorylated AP-1 (p-AP-1) and NFATc1 protein were detected by Western blot in each group. The fluorescence expression of TRAF6, p-JNK, p-AP-1 and NFATc1 were detected by immunofluorescence assay in each group. Results (1)Compared with control group, the expression levels of TRAF6, p-JNK, p-AP-1 and NFATc1 protein were significantly increased in CD137 stimulation group (CD137-CD137L signal activation) (P＜0.05). Compared with CD137 stimulation group, the expression levels of TRAF6, p-JNK, p-AP-1 and NFATc1 protein were significantly decreased in CD137 inhibition group (CD137-CD137L signal inhibition) (P＜0.05). (2)The siRNA technology was used to silence TRAF6, JNK and AP-1 respectively. Compared with CD137 stimulation group, the expressions of TRAF6, p-JNK, p-AP-1 and NFATc1 were significantly reduced in siTRAF6 intervention group (P＜0.05); The expression of TRAF6 had no change, while the expression of p-JNK, p-AP-1 and NFATc1 were significantly decreased in siJNK intervention group (P＜0.05); The expressions of TRAF6 and p-JNK had no significant change, while the expressions of p-AP-1 and NFATc1 were significantly decreased in siAP-1 intervention group (P＜0.05). (3)Immunofluorescence assay showed that the fluorescent expressions of TRAF6, p-JNK, p-AP-1 and NFATc1 were increased in CD137 stimulation group (P＜0.05), and the fluorescent expressions of TRAF6, p-JNK, p-AP-1 and NFATc1 were significantly decreased in CD137 inhibition group (P＜0.05). The fluorescent expressions of TRAF6, p-JNK, p-AP-1 and NFATc1 were consistent with the above protein expressions in siTRAF6 intervention group, siJNK intervention group and siAP-1 intervention group. Conclusion CD137-CD137L signal can affect the expression of NFATc1 through the TRAF6/JNK/AP-1 pathway.