Abstract: Objective To analyze the expression characteristics of mRNA of complement-related genes in patients with symptomatic pulmonary embolism(PE). Methods The whole human genome expression profile chip was used to analyze the expression differences of mRNA of complement-related genes in 20 PE patients and 20 controls. Results (1) There were 21 genes of complement intrinsic component. Compared with the control group, the expression of C5 mRNA increased significantly in PE group(P<0.05), the expressions of C1QA, C1QB, C4B and CFP mRNAs increased significantly in PE group(P<0.01), and the expression of C6 mRNA significantly decreased(P<0.01). (2) There were 7 complement receptor genes in PE group, and the mRNA expressions of CR1, ITGAX, ITGAM and C5AR1 in PE group were significantly higher than those in control group(P<0.01). (3) There were 7 complement regulatory protein genes in PE group. Compared with the control group, mRNA expressions of CD59(P<0.05)and CD55(P<0.01)increased significantly in PE group, while mRNA expression of CFI decreased significantly(P<0.05). Conclusion The imbalance of mRNA expression of complement intrinsic component, receptor and regulatory protein gene in PE patients suggests that the immune function of complement is disordered and(or)defective, which eventually leads to the decrease of membrane dissolving ability mediated by complement.