The expression of complements C1R, C1S, C2, C5, CFB, CFI, C8A, C9, CR4 (ITGAX), C5aR1, C1INH, C4BPA, C4BPB, CLU, CD46, CD55, CPN1, CRIg, and C1qR was significantly higher in CRC samples, while the expression of complements C1S, C3, C6, C7, C8B, CFD, CFP, CFHR1, CFHR2, CFHR3, CR1, CR2, CR3 (ITGAM), C3aR1, C1INH, MASP2, MASP1, CLU, CD55, CD59, CRIg, C1qR, and SIGN1 was lower in CRC samples than that in normal tissues. The gene discussed is C3AR1; the disease is colorectal carcinoma.