【Abstract】〓Objective〓To construct the small interfering RNA of ICAM1 cell ICAM1, and to explore whether specific siRNA could inhibit the expression of ICAM1 induced by LPS in A549 cells. Methods〓 Human type 2like alveolar epithelial cells (A549 cells) were examined for expression of ICAM1 after treated with lipopolysaccharide (LPS). SiRNA to target human ICAM1 was synthesized. After transfected with non viral siRNA, A549 cells were treated with LPS. ICAM1 expression was measured by flow cytometry and RTPCR. Results〓 The expression of ICAM1 on A549 cells was induced by LPS. But cells were damaged in high LPS concentration. Compared with the OD value of 10 ng/mL LPS group and 100 ng/mL LPS group, there were significant differences between the two groups (P＜0001). After treated with 10 ng/mL LPS for 8 h or so, there was no obvious damage to the cells. After treated with 10 ng/mL LPS for 1 h, the expression of ICAM1 mRNA was upregulated (P＜005). But the expression of ICAM1 protion was no significant difference. After treated with 10 ng/mL LPS for 4 h, the expression of ICAM1 mRNA and protein were upregulated too(P＜005). Nontransfected cells showed a strong increase of ICAM1 expression following LPS stimulation. SiRNAmediated gene suppression of ICAM1 was also reflected by corresponding decreases in protein and transcript levels. Conclusion〓 The expression of ICAM1 on A549 cells can be effectively inhibited by specific siRNAs using a nonviral transfection approach.