Abstract: The starting material 2- chloro- 4, 6- diamine- 1, 3, 5- triazine ( CAAT) reacted with 6- aminocaproic acid ( ACS) to create a hapten Mel- ACS, then this hapten was conjugated with bovine serum albumin ( BSA) to form BSA- ACS- Mel, which was supposed to have a connection arm and would be used as an antigen for the preparation of monoclonal antibody ( m Ab) . Antigenic characteristics analysis by HPLC, Western blot and ELISA proved that the yield of hapten Mel- ACS reached 85.9% and specific monoclonal antibodies against Mel reached42.9%.The antigen BSA- ACS- Mel had good immunogenicity and can be applied to detect melamine molecule specifically.This method played a guiding role in the synthesis of other small molecule antigens.