Factor C is a serine protease enzymogen presented in the circulating blood cell of horseshoe crab. Owing to its extreme sensitivity to endotoxin, Factor C (FC) plays an important role in pyrogen-detection in pharmaceutical products. Previous study has shown that three Sushi domains (S123) in the N-terminal of FC are critical for its LPS-recognition activity. The effect of three other domains in N-terminal of FC, namely Cys-rich, EGF-like and Lectin-like, on its LPS-neutralization function was not clear. The recombinant FC and its four truncated fragments were expressed using Bac-to-Bac baculovirus expression system in Tn cells. The five recombinant peptides were then purified and tested for the LPS-binding activity and bactericidal activity in vitro. The experiments showed that the LPS-binding site of Factor C resides in the S123 region. Even though Cys-rich, EGF-like and Lectin-like domains do not harbor LPS-binding site, the presence of all three domains can improve LPS-binding activity of S123. Recombinant peptide rCES123L containing Cys-rich, EGF-like, S123, and Lectin-like domains exhibits almost the same LPS-binding activity as that of the full-length parental FC. Provided the fact that rCES123L has 4-fold higher production yield than that of recombinant FC in Tn cells, this peptide has a potential in biotechnology and pharmaceutical application for LPS-neutralization.