To investigate the relationship between the natural killer T (NTK) cells level in peripheral blood of preganant women and their incidence and severity of intrahepatic cholestasis of pregnancy (ICP). Methods: 52 pregnant women with ICP were enrolled and were divided into group A (28 women with mild ICP) and group B (24 women with severe ICP) from March 1, 2016 to March 1, 2018. Meanwhile, 52 healthy pregnant women during the same gestational weeks were randomly selected in group C. The level of NKT cells in peripheral blood mononuclear cells (PBMC) of women were compared among the three groups. The correlation between NKT cell level and ICP occurrence and development was analyzed. Results: The peripheral blood NKT cell level in PBMC of women with ICP was significant higher than that of healthy pregnant women (P＜0.05). The peripheral blood PBMC of women in the three groups was cultured by different stimulants, and the NKT cell level had no significant different between the women in group C and the women with their PBMC cultured no stimulants (P＞0.05). The NKT cell level of the women with their PBMC cultured by phytohemagglutinin stimulants, the women with ICP, and women in group C had decreased in turn (P＜0.05). The peripheral blood NKT cells level in PBMC of women in group B was significant higher than that of women in group A (P＜0.05). The NKT cells level of women with ICP was positively correlated with the severity of ICP (P＜0.05). Conclusion: The occurrence and progression of ICP is positively correlated with the level of NKT cells in the peripheral blood of pregnant women, so monitoring the level of NKT cells maybe provide a new idea for diagnosing ICP.