Aim To investigate the effects of leptin on the expression of interleukin-1β (IL-1β) in macrophages in vitro. Methods RAW264.7 cells were incubated with leptin in different concentrations (1.25, 2.5, 5, 10 nmol/L) for 4 hours, reverse transcription polymerase chain reaction (RT-PCR) was used to measure the expression of IL-1β mRNA level; Meanwhile, RAW264.7 cells were incubated with these concentrations of leptin for 1, 3, 6 and 9 hours, then the expression of IL-1β in the medium was determined by enzyme linked immunosorbent assay (ELISA). Results The expression of IL-1β mRNA was promoted with the concentration of leptin (0.107±0.102, 0.204±0.019, 0.718±0.083, 0.642±0.071), and reached the maximum level at 5 nmol/L of leptin. At the same time, the expression of IL-1β protein was promoted with the concentration and the time of leptin stimulating, and reached the maximum at 6th hour (p<0.05). The expression of IL-1β in both mRNA and protein levels in RAW264.7 cells incubated with leptin were increased with the leptin concentration. Conclusion Leptin can increase the IL-1β expression of RAW264.7 cells directly and that might be one of mechanism of atherosclerosis induced by leptin.