Objective To analyze the antigen recognition sites of commercial and homemade antibodies against aquaporin (AQP) 9 ，and to identify the application effect.     Methods Western blotting was used to compare the efficacy of three commercial antibodies and self-made antibody in identifying AQP9 genotypes. The antigen recognition sites of four antibodies and their specificities in practical applications were analyzed.   Results Western blotting showed that protein bands of three commercial antibodies were detected in both WT and Aqp9^-/- mice. The keyhole limpet hemocyanin(KLH) conjugated synthetic peptides corresponding to the three commercial antibodies were derived from rat, human and human, respectively. And The sequences of these three synthetic peptides were different from those of mice. AQP3/7 and AQP9 have similar molecular weight and were expressed in the liver with high homology. An obvious band of self-made antibody was observed at the 27 kD position in WT mice, but no band was observed at the corresponding position in Aqp9^-/- mice.   Conclusion Commercial antibodies 1 and 3 can be used to assist in the identification of genotypes in Aqp9^-/- mice. Homemade antibodies can accurately identify genotypes at the protein level.