In order to study the effects of LDL and oxLDL on expression of PCSK9 and LDLR in THP-1 macrophages and find the relationship between them. THP-1 cells were induced to differentiate into macrophages by PMA treatment. Cells were then co-incubated with LDL or oxLDL with a concentration of 0 mg/L, 10 mg/L, 20 mg/L, 30 mg/L for 24h respectively. Cellular lipid was visualized by oil red O staining. The localization and semiquantitation of PCSK9 was confirmed by immunofluorescence assay，the expression of PCSK9 and LDLR was analyzed by RT-PCR and Western blotting. Oil red O staining showed that a number of visualized lipid droplet accumulated within THP-1 cells. The lipid droplet is big and accumulating in cells co-incubated with oxLDL but small and dispersing when co-incubated with LDL. Matured PCSK9 are expressed on the cell surface and some organelle, and increased with the increasing of LDL concentration through immunofluorescence assay. RT-PCR, Western blot showed that, in THP-1 , LDLR was downregulated while PCSK9 was upregulated especially when treated with LDL , but the treatment of low concentration of oxLDL likely had no effect on expression of LDLR and PCSK9. Together, these results reveal that PCSK9 and LDLR may co-expressed in THP-1 cells, which are unable to be influenced by oxLDL, but may be down-regulated (LDLR) or up-regulated (PCSK9) by LDL, providing primary evidence of the correlation between PCSK9 and LDLR.