The retarding side effect and the compatibility with other additives are the main problem to limit the field application of the fluid loss control additive (FLCA) synthesized. The effect of the type and content of carboxylic acid group on the retarding side effect of FLCA and the compatibility between FLCA and the retarder AMPS-IA synthesized by 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and itaconic acid (IA) was studied in this paper. The type and content of carboxylic acid group have a great influence on the fluid loss control ability, the compatibility with retarder and the retarding side effect of FLCA. FLCA containing IA or maleic acid (MA) shows better compatibility with retarder than FLCA containing acrylic acid (AA), but the retarding side effect of FLCA containing MA is weaker than that of FLCA containing IA, so MA is the most suitable monomer to synthesizing FLCA having good compatibility with retarder AMPS-IA.