Anti rat amniotic protein antibody was developed by immunization of rabbits with total rat amniotic protein as antigen in Freund's adjuvant. This antibody could react with both male rat serum and amniotic proteins. To obtain the pure anti AFP antibody, rabbit anti serum was loaded on an affinity chromatography column which contain agarose, activated by carbodiimide, and male rat serum protein immobilized. Eluat containing protein that was not reacting with immobilized male rat serum was collected in 2 mL fractions. Each fraction was measured. The first 8 fraction give a peak. The range of protein concentration were about 0,35 - 4,51 mg/mL. The range of anti rat .AFP antibody titre were 40 - 1280. The conclusion is that the anti rat amniotic protein antibodies contain the antibody againts rat AFP. The anti rat AFP antibody could reacted or detected the AFP in amniotin fluid proteins that was not in the adult male rat serum. The conclusion is that the anti rat amniotic protein antibodies contain the antibody againts rat AFP. The anti rat AFP antibody can react or detect the AFP in the amniotic fluid protein that is not in the adult male rat serum.